NBC moved away from cartoons long ago. They found more syndication money in programs like “Saved By The Bell” which weren’t restricted to just “weekday mornings and afternoons”.
ABC is owned by Disney and Disney needs lots of programming for their cable/video empire (and new marketable characters).
But even cable and satellite channels like Cartoon Network don’t seem to show the old classics too much anymore. I’m sure it’s due to pressure from the “PC” left. The same left who wants to indoctrinate our kids with their left-wing political BS every chance they get.