In the late 90s, there was something of a massacre of the golden age of Warner Bros TV animation, and the start of a shift in Warner animation. This is blamed on Jamie Kellner, the CEO of Turner Broadcasting. Kellner cancelled Animaniacs, Pinky and the Brain, and Freakazoid in a fell swoop. Before that, he forced Pinky and the Brain to retool to that godawful "Pinky and the Brain and Elmyra", which was the incarnate version of the "Pinky and the Brain and Larry" parody the people behind Pinky and the Brain did. If you've never seen it, it was in reaction to corporate requests to add a third character, and the production showing that the chemistry was between Pinky and the Brain and a third character ruined it and was totally out of place. He also oversaw the cancellation of Earthworm Jim, Batman the Animated series, the Superman animated series, etc. Certain of those listed can be said to have run their course, but many of them were killed while still very, very popular so the reason was just because evidently (at least from what I've read) Jamie Kellner just didn't like them in spite of their popularity and wanted to change the tone and target audience. Those were killed to bring in 4Kids productions and anime, and that was the shift.
So what if that kind of policy was not adopted, and Animaniacs et al were allowed to run their course?