The supermarket is an adventure for Shonda Rhimes.

"I go to the grocery store, and at almost every point I find a group of 12- or 13-year-old girls staring at me," said the woman whose TV shows are the backbone of ABC's Thursday night lineup. The gawking might be expected of the 18-to-49 demographic hooked on "Grey's Anatomy," "Scandal" and "How to Get Away With Murder." But the attention from this younger generation of fans points directly to how Ms. Rhimes and her production company, ShondaLand, are drawing in Netflix- and Hulu-weaned youngsters who were toddlers when "Grey's" hit primetime. These viewers, she said, are watching more than 200 older episodes to catch up on the storylines, and then tuning in to see new ones live on ABC.

About 200,000 viewers watched the pilot episode of "Grey's" on a range of platforms in recent months, according to the network, citing Nielsen estimates.

Astoundingly, 11-year-old "Grey's" is also on pace to end this season as ABC's No. 1 series. And it's not just ABC viewers, but also the network, thanking God it's Thursday. Ms. Rhimes has been described as "the Charles Dickens of the 21st century" by former ABC entertainment head Paul Lee, and at this year's National Association of Broadcasters conference in Las Vegas, Disney/ABC TV Group President Ben Sherwood put her value to ABC on par with Elvis Presley's importance to Sin City.

While the shows Ms. Rhimes produces, runs or created aren't immune to the downdraft of TV ratings, they are holding up better than most. ABC's all-Rhimes TGIT block remains among the few hours outside sports that viewers consider event TV, even as more and more people shift viewing to fit their schedules.

As such, her series are giving the network more leverage in the approaching upfronts than it would otherwise merit. Now, she's ready to turn her success thus far into a bigger, broader empire, seeking new genres, bringing new writers into the fold and expanding beyond traditional TV.

The challenge will be to take her proven formula to new places without losing that essence of ShondaLand. "I'm at a crucial point right now," Ms. Rhimes said. "ShondaLand is at a crucial point."

You could say the same for TV itself. Audiences keep shrinking or, at best, watching in places that Nielsen doesn't yet track. Networks are renewing shows that they would have quickly canceled just five years ago. Marketers still pour ad dollars into the medium; broadcast and cable upfront commitments this summer will likely total more than $20 billion. But at the same time, advertisers are glancing around, ready to ditch traditional commercials as soon as something better comes along.

In this world, ShondaLand can feel like an oasis.

"It's been a challenge to make programs on broadcast, with all of its limitations, that are hip to watch," said Robert Thompson, professor of popular culture at Syracuse University, who likens Ms. Rhimes to programming giants of the 1970s and 1980s like Aaron Spelling and Garry Marshall. "In the second decade of the 21st century on broadcast, it really is a feat that she has been able to continue making programming that is contemporary and relevant. Her shows bring a wonderful period of nighttime soap operas, like 'Dallas' and 'Dynasty.'"

As creator and showrunner for "Scandal" and "Grey's," plus executive producer of "How to Get Away With Murder" and new midseason drama "The Catch," Ms. Rhimes has made her mark so far with contemporary hour-long serials.

But ABC has just picked up a different kind of hour, a period drama based on "Romeo and Juliet." Set in 16th-century Verona, "Still Star-Crossed" explores what happens to the families of Romeo and Juliet after the young lovers die. That means Ms. Rhimes will have five shows on ABC next season, three of which were not created by her, and her ambition doesn't stop there. Although ABC passed on it late last week, ShondaLand had pitched a pilot for its first comedy series, an entirely new genre for the company.

ShondaLand may also look beyond traditional TV for future projects. "Network television has obviously been very good to me and I love it, but there are a million other ways to tell stories now that are out there that are fascinating and I think monetizable and audiences can get really excited about," Ms. Rhimes said.

Smaller screens, the ability to release 15 episodes at once and the flexibility to create episodes outside of the 30-minute or one-hour window all appeal to Ms. Rhimes. She may even try her hand at virtual reality. But she declined to elaborate further on any of that.

As ShondaLand grows into a hub for a plethora of voices creating content for a variety of screens, Ms. Rhimes will have to balance expansion with maintaining her recognizable, marketable voice. "You can spot a Shonda Rhimes show from miles away," Mr. Thompson said.

"It has been really important to find shows that feel like our brand, that sound like our brand, because I want audiences to continue to depend on the fact that if it is a ShondaLand show, they know what they are getting," Ms. Rhimes said. "You are not going to wonder what this is going to be and be really disappointed because we have jumped outside the box."

This dependability is attractive to advertisers, who are willing to pay top dollar to be part of TGIT. Both "How to Get Away With Murder" and "Scandal" are among the 10 costliest programs for advertisers, according to Ad Age's 2015 pricing survey. A 30-second spot in either of the shows costs upward of $200,000.

Marketers are attracted to TGIT's upscale audience, which is highly engaged with the shows on social media. The diversity of the programming, both in casting and storylines, also appeals to advertisers seeking content that better represents America.

Ms. Rhimes is intimately involved in creating integration opportunities. "I actually feel like I pitch more stuff than the network wants to use sometimes," she said.

While she surely isn't the first showrunner to have multiple programs on a network at one time, Ms. Rhimes' name, more than even some of the most prolific showrunners, has turned into a very recognizable and marketable brand.

It makes a difference to say something is a Shonda Rhimes show, said David Campanelli, senior VP-director of national broadcast, Horizon Media. "You know the quality of the show and know what to expect. It is easier to justify to a client betting on something when you have a name like that to go with it. It is a name that matters more than the show. That's rare and she is one of those cases."

Ms. Rhimes has adroitly redefined gender, sex and race on TV. The protagonists of her shows are powerful, flawed and incredibly complicated women. Her nighttime soaps may not have the same cachet as the broody serials over on cable, but her characters exude antihero characteristics like Walter White's on "Breaking Bad": It's never exactly clear who's wearing the metaphorical white hat. Nor is Ms. Rhimes afraid to shed some on-screen blood, keeping up with cable in that regard and earning her the label "character murderer" among some fans.

In this way, Ms. Rhimes has upended the long-standing premise that network TV can't compete with the creativity of cable. And for anybody counting, more people watched "Grey's Anatomy" live last week than the finale of the critically acclaimed "The People v. O.J. Simpson" on FX live and in the three days after it aired.

Ms. Rhimes hasn't done this by setting out to purposely shock people. Despite the monumental changes that have disrupted the TV model in the 11 years since "Grey's Anatomy" debuted, Ms. Rhimes hasn't deviated from her hit-making strategy. For her, staying true to her creative process, and quite simply telling good stories, supersedes any concerns over viewer fragmentation or cord cutting.

"I honestly feel like I've kept doing things pretty much the same way," she said. "The secret sauce of the business that I can offer is my creativity, and in order to keep my creativity alive and fresh ... I have to pretend that no one is watching the show, that there are no audiences, there are no ratings, I'm just telling a story."

ABC introduced TGIT in fall 2014, harking back to the network's wildly popular TGIF family comedy lineup of the 1980s and 1990s.

By assembling ShondaLand's drama trio back-to-back-to-back, ABC set out to convince viewers to not only watch three hours of TV, but to watch them live and all on one network. That's no easy task in the current environment.

To help it work, ABC has aggressively marketed the programing block, playing up the OMG factor that drives social media chatter.

And Ms. Rhimes has helped fan the online conversation. Even before Twitter ("Grey's Anatomy" debuted a year before the platform launched), she was blogging with fans at the end of every episode.

Now Ms. Rhimes, who boasts 1.2 million Twitter followers, and the casts of her series interact with fans during the episodes, host live viewing parties and experiment with platforms like Periscope and Facebook Live.

It seems to be working: TGIT accounted for three of the top 10 scripted shows on broadcast among the 18-to-49 demographic last year.

"TGIT as a brand itself has become stronger than some cable channels," said Andrew Kubitz, head of scheduling for ABC, noting that ShondaLand shows have been a "perfect match" for the lineup. And whether or not it was ABC's intention, TGIT has also become synonymous with Ms. Rhimes.

While Mr. Kubitz was abundant in his praise for Ms. Rhimes and ShondaLand, he was also careful to downplay TGIT's long-term reliance on ShondaLand shows.

Of course, ABC will continue to bring in new projects from the company -- ShondaLand's current deal with ABC is not set to expire for another two years -- but Mr. Kubitz said there won't only be ShondaLand shows on TGIT.

"We see Thursday night as a viewership opportunity, with either couples or women by themselves who want to sit down and escape and have fun and drink their red wine and have some popcorn," he said. "Right now, Shonda shows are the ones that are resonating with that [group], but that doesn't mean any other show we are developing now or in the future can't fit within that TGIT brand."

Those new shows could even come from some of the leading ladies in Ms. Rhimes' own dramas. ABC Studios recently signed deals with Viola Davis of "How to Get Away With Murder" and Kerry Washington of "Scandal" to develop new projects for broadcast, cable, streaming services and digital platforms.

ABC certainly needs to find some new voices. While Ms. Rhimes' shows carry their weight, they've suffered ratings erosion like most others.

"Scandal" is down 28% in the 18-to-49 demographic this season to date, while "How to Get Away With Murder" has plunged 37%. And "The Catch," ShondaLand's newest entry, is averaging a disappointing 1.0 rating in the demo since debuting in March.

Ms. Rhimes said she doesn't follow the ratings of her shows. "I stopped paying attention to the ratings, I would say, maybe a year into 'Grey's' when I realized I have no control over the ratings."

ABC, on the other hand, is paying very close attention. It is on track to end the season last among the Big Four broadcasters among 18-to-49-year-olds, averaging a 1.8 rating in the demo, down 18% from last season.

The network didn't have much luck with its most recent freshman series: Its now-cancelled "Muppets" reboot flopped despite significant fanfare; "Blood & Oil" had its episode order cut; quick cancellations for "Wicked City" and "Of Kings and Prophets" left Tuesday's 10 p.m. time slot a mess; and even "Quantico" has faded after a promising start. (It doesn't help that ABC lacks NFL programming, one of the juggernauts of today's TV landscape.)

The network also made the decision last week not to renew "Nashville," "Catle," "Galavant," "Agent Carter" and "The Family."

ABC has renewed all four of Ms. Rhimes' current shows for the 2016-17 season.

Mr. Kubitz attributed ABC's ratings weakness in the 2015-16 campaign to the dramatic decline in viewership for returning series across broadcast TV, as audiences try the cornucopia of new content available not only on TV but on other platforms.

ABC brought back 24 shows this season, more than any other broadcaster, so "we were more adversely affected," Mr. Kubitz said. CBS renewed 22 shows, Fox brought back 15 and NBC renewed 13.

"But like with 'Grey's,' we have found [viewers] might go and experiment elsewhere, but when you create consistent, great content, you can bring them back, and that's what our goal is for next season," he said.

Indeed, "Grey's Anatomy" is exhibit A for the promise of that plan, having bucked the odds in the 2015-16 season to average a 2.2 rating in the 18-to-49 demographic. The show currently ranks as the No. 2 returning broadcast drama in the demo, behind only the Fox phenom "Empire."

And while "Grey's Anatomy" is still down 7% in the demo over last year, that counts as relatively stable when other returning series have fallen by double digits.

The show's success owes in large part to a new generation of fans discovering the series on Netflix and Hulu, according to Ms. Rhimes. Viewers as young as 12- or 13- years-old, who weren't even born when the show started, are watching over 200 episodes to catch up and then tuning in live on ABC, Ms. Rhimes said.

Despite this phenomenon, Ms. Rhimes isn't thinking about how people might watch her shows when she is developing them. "I am not writing or creating for the binge-watching experience," she said.

Mr. Kubitz said he hopes the network can revive some of its longer-running shows in the same way it has with "Grey's Anatomy." There are also plans to lean heavily on the success of its family comedies.

ABC's next-season lineup, which it will detail at its upfront presentation on Tuesday, is the first glimpse into the alphabet network's programming strat- egy under Channing Dungey, its newly appointed enter- tainment president. Ms. Dungey, who has been credited with developing some of ABC's most successful dramas, including those from Ms. Rhimes, replaced Paul Lee in February to become the first African-American to head programming at a major broadcast network.

Ms. Rhimes has known Ms. Dungey since she was a "baby executive" in the early days of "Grey's Anatomy."

"She is a person whose opinion I think very highly of," Ms. Rhimes said. "I think it is wonderful to have someone like her in charge because she is very creative, she is very smart, she has a smart handle on what the audiences are looking for and she has been there for a long time."

Ms. Dungey declined to comment for this piece.

ShondaLand, however, ultimately couldn't sell ABC on the sitcom "Toast." Despite entering new territory for the company, the pilot still felt like a ShondaLand show, according to Betsy Beers, Ms. Rhimes' production partner. ShondaLand has been eyeing the comedy genre for some time, and Ms. Beers said the company is committed to establishing a presence in the genre.

"Still Star-Crossed," the take on "Romeo & Juliet," is also a new path. "It's a very different show than we have ever had on the air before," Ms. Beers said.

Both Ms. Rhimes and Ms. Beers continue to believe the TV model works.

"The idea that you can keep a crowd of people together and breathless and then make them all wait another week while they spend the week going, 'What do you think is going to happen?' -- which we all did while watching 'The People v. O.J. Simpson' -- is still possible," Ms. Rhimes said.

Ms. Beers said there's an intimacy that occurs with TV "that is very special and very intense and just very personal." And despite the "doom and gloom predictions" of the death of TV, it is all "greatly exaggerated."

Still, Ms. Rhimes, who published her first book in November, "Year of Yes: How to Dance It Out, Stand in the Sun and Be Your Own Person," is excited about growing ShondaLand into a brand that does more than "just make television shows."

One place you likely won't see Ms. Rhimes is leading a TV network. "I can't ever say never, but right now I can't imagine the idea of wanting to go work at a network because I don't want to get behind a desk all day," she said. "That is not really where my passion lies."

"I am busy exploring what that brand can be … and it is definitely not just the idea that there will be more TV," she said.