It’s interesting to me that some perceive “Saturday morning cartoons” ending circa 1980. I can assure you that they were still going great guns during the Reagan era. Do the titles The Smurfs, The Care Bears, SuperFriends, Rainbow Brite, and Strawberry Shortcake ring any bells?
Just some data points from a dad of now-teenagers: There were certainly Saturday morning cartoon blocks on one or more of the Big Four broadcast networks as recently as 2009. Some of the titles included Sonic the Hedgehog, Dino-Squad, and Winx Club.
Additionally, some PBS cartoons such as Sagwa and Arthur were shown in a special Saturday Morning block on CBS. The last time I can recall watching those were in 2005, when my oldest was a toddler.
If you’re asking me, one of the things that for sure led to the decline of Saturday morning cartoons was simply the round-the-clock glut of animated content available to kids. I remember the after-school “toy commercial” cartoons such as He-Man, GI Joe, and Transformers in the 1980s. But that was nothing compared to what my kids grew up with: 12 hours a day of Noggin (later Nick Jr.), 24 hours of Disney Channel (some live shows), 12-15 hours a day of PBS cartoons with many markets having a separate PBS Kids channel, etc. And that’s just scratching the surface of what was on TV circa 2000-2009: animated programming also aired on Cartoon Network, Boomerang, Discovery Kids, Hub, etc. And on top of THAT were the legion DVDs and legacy VHS tapes of all kinds of cartoons and kids fare.
Ergo … Saturday mornings ceased to be “appointment television time” for kids anymore. They could and did watch it all the time.