One Way I'd Improve this Film/Guess who Oriana looks like?

Polish up the animation, remove half the background noise, tone down Felix dialogue near the beginning of the movie, fix the ending, plus what you said about Pearl and Grumper...boom, good movie.

I have to wonder why Disney didn't touch up the movie considering they aired it on their channel for so long and promoted it a fair bit in the early 90's.

For me, the main issue is simply that the world they created is simply too dark for this type of protagonist. It's basically Heavy Metal for kids. This should be an alternate dimension in an animated movie adaptation of the Teenage Mutant Ninja Turtles, not something starring a chipper feline protagonist with a fixed smile on his face.

They could have kept the basic plot intact. They just needed to tone down how dark and dismal that world was. That, or they could have waited until after they had done Felix the Cat and made an entirely different film with all of this film's mutations and disfigured villains.