It’s funny that the reason you give for the cancellation of Batman: The Animated Series was exactly the same reason I saw given when The Adventures of Pete and Pete was cancelled. I remember reading an article at the time Pete and Pete went off the air that some Nick executive said it would be too costly to do a new season when their research showed that kids will watch the same episodes over and over.
I thought that was a pinhead point of view then and I still think so.
Step By Step (ABC / Part of Classic TGIF Block) Pretty much couldnt recover from Sasha Mitchell’s ( Cody ) Domestic Abuse. Hard for me to picture the Code-Man hitting his wife/GF but apparently, if memory serves me, he did, and got arrested. This was explained I bet, and Suzanne Sommers and Patrick Duffy had a kid, (Libby?) and Branson Pinchot (Unlce Luc) were called in. For me, the show lost nearly everything at that point.
Family Matters (ABC Also Part of TGIF) stopped I think because Jaleel White ( Urkel // Stephan ) wanted to stop. And good call on his part. Urkel ((Which was to be a one episode chracter)) carried the show just past its shelf life.
IIRC, the show got bumped over to CBS for its last season, they replaced the actress who played Harriette (but not the character, a 'la Becky on Roseanne), and I’ve read several bits of trivia that said the cast was unaware the show would be ending after the ninth season and only found out after CBS had destroyed the sets.