Network TV starting "relaxing it's censorship" several years ago when it noticed HBO and Showtime along with other pay cable channels content were getting much better reviews by critics and taking home the lion share of Emmy awards each year.
Secondly advertisers have made it known they want to advertise on shows that draw the coveted ages 18-49 demographic audience.
Therefore you might have a show like "NCIS" be ranked #1 overall however a show like "Empire" which is #1 for age 18-49 is seen as being the show other networks will want to emulate.
Young children and adults over the age of 50 are not the "prime" demographic. Their shows are usually on TV earlier in the day.
For those with cable they also have the option of stations like "Me TV" where they show old TV shows from the 50s, 60s, and 70s.
There is also "Tuner Classic" which shows old Hollywood black and white movies. Odds are if you have 200-300 channels you can find something you enjoy in any given hour.
When it's all said and done network TV is in business to make money.
Should ever the viewing audience ages 18-49 show a preference for shows like "Happy Days", "Mork and Mindy" or "Columbo" odds are the networks would RUSH to produce similar shows.
People vote with their remote.
Having said that most programs will feature a screen stating "Viewer Discretion Advised" or list age recommendations along with content bullets spelling out this show contains violence, nudity, or "strong" language...etc