The state and future of animation

[Randall]

They hadn't run out of ideas yet.

[Ben]

Because you can’t top pigs with pigs.

This.

[EricJ]

Why did animation studios have a "no sequel policy" through the 1990's. The existence of theatrical sequels like The Rescuers Down Under, Fievel Goes West, and All Dogs Go To Heaven 2 seem to show otherwise.

"Studios" didn't (and Universal clearly didn't), Disney did:
After Disney's direct-video OVA market had been abused just like Disney's current live-action mania (ie. using them just to jumpstart the market for forgotten titles), John Lasseter put his foot down and banned any title-IP project that specifically pretended to follow the events of the classic movie.
Which threw ToonStudio's Tinker Bell movie into a last-minute tailspin, but things worked out.

And to answer your next question, this was in the 00s.

[Ben]

And, so, not related to the original question…