“That is an infinite loop we believe in,” said

Mark Lazarus,

chairman of Comcast Corp.’s NBCUniversal Television and Streaming, which operates NBC and the Peacock platform. “We are able to move our audiences through our services.”

Walt Disney Co.’s ABC points to the success of its new, Emmy-nominated comedy “Abbott Elementary” as an example of the role of broadcast networks in 2022. “We were able to use the reach of ABC to launch a show like ‘Abbott,’ then it went to Hulu, where it picked up a sizable group of different viewers and doubled its audience,” said

Dana Walden,

chairman of Disney General Entertainment Content, which includes ABC, Hulu and the company’s television-production studios.

Both ABC and NBC went one step further: Moving some of their best-known shows to streaming platforms to give them a boost.

NBC is moving its daytime soap opera “Days of Our Lives” exclusively to Peacock starting Monday, while Disney is putting ABC’s long-running hit “Dancing with the Stars” on Disney+.

“You need to go where the audience is,” said former CBS Entertainment President

Nancy Tellem.

“The consumer is now in control, not the networks.”

“The relevancy of broadcast TV has been declining for years,” said

Jeff Gaspin,

a former top executive at NBC who is now a producer. “I suspect nobody is making money in prime time.”

The parent companies of ABC, CBS NBC and Fox don’t disclose financial results for their broadcast networks, instead combining them with other television operations.

Of the new shows networks are launching, several will give viewers a sense of déjà vu. NBC is rebooting its 1990s series “Quantum Leap,” while ABC has a spinoff of its police drama “The Rookie” about a newbie FBI agent. It’s called “The Rookie: Feds.”

They will join a prime-time schedule littered with offshoots of existing programs and new versions of old shows. NBC has numerous “Law & Order” and “Chicago” variants. CBS has its “NCIS” and “FBI” franchises.

Part of the reason for all the cookie-cutter content is that much of networks’ loyal audience—viewers over the age of 50—favors more traditional crime and legal dramas. Such shows also tend to repeat better than the more complex serialized shows that fill cable networks and streaming services.

“If I’m being candid, I’m not looking to find a $20 million-an-episode premium drama,” said CBS Chief Executive

George Cheeks.

Mr. Cheeks said his network’s primary role is to be the first stop on the content conveyor belt of parent Paramount Global, whose streaming platforms include Paramount+ and Showtime Now.

The ground has shifted so much that NBC is considering no longer programming the 10 p.m. hour, once home to prestige dramas such as “ER” and “Hill Street Blues.” Its affiliates would instead carry local programming, most likely news. NBC would also then start late-night programming like “The Tonight Show Starring Jimmy Fallon” earlier, people familiar with the matter said.

Broadcast networks’ second-class status will likely be particularly apparent during the Emmy Awards, which are this Monday on NBC. Once a showcase for ABC, CBS, NBC and Fox, the show now usually showers its biggest prizes on HBO,

Netflix,

Apple

and Hulu.

With ratings in precipitous decline, especially among younger viewers sought by advertisers, networks are shifting spending away from entertainment and toward sports, which can draw a big audience and serve as a promotional platform for other programming.

Excluding sports, CBS was the only network to average more than five million viewers last season. Over the past five years, the collective average audience for the big four networks outside of sports has fallen 33% to 17.5 million viewers, according to Nielsen. During the same period, streaming services have accumulated tens of millions of subscribers among them.

Former Disney Chairman and Chief Executive

Robert Iger

warned this past week at the Code conference that traditional TV is “marching to a great precipice, and it will be pushed off.”

One of his former colleagues disagrees—at least when it comes to his old company.

“While it’s indisputable that the television industry remains in the midst of tremendous disruption, there are companies that are making better sense of the business than others, and Disney is one of those companies,” Ms. Walden said.

Fox is something of an outlier. It already programs fewer hours than the other networks and is also mostly staying out of the streaming wars. It sells shows to Hulu and owns Tubi, a free, ad-supported streaming service that focuses on lower-budget original programming, along with old movies and TV shows.

What Fox doesn’t want to do is build a high-end subscription streaming platform and spend the way Netflix, Apple, Disney and others do on original streaming content.

“If you look at the biggest streamers, collectively they launched more than 2,000 series, and of those, approximately 15% were seen by a million people,” said Michael Thorn, Fox’s entertainment chief.

Fox Corp.

and Wall Street Journal parent

News Corp

share common ownership.

NBC is considering a reduction in the number of prime-time hours it is responsible for programming to 15 from 22, but NBC’s Mr. Lazarus said that it is still investing heavily in sports for the network. It struck a deal with the Big Ten Conference to carry college football for the next seven years, giving the network a pipeline of premium content for hours that are currently treated as an afterthought.

“Instead of running repeats and movies on Saturday night, we’re now going to have high-profile, highly rated content,” Mr. Lazarus said.

Given the amount of competition and the difficulty of creating even modestly successful shows, Ms. Tellem questions why ABC, CBS and NBC haven’t already cut back.

“Who wrote that we had to have 22 hours?” she said. “It’s not etched in stone.”

Write to Joe Flint at joe.flint@wsj.com