I wouldn't miss any of the following:
MAGIC KINGDOM
- The Enchanted Tiki Room Under New Management
- The Many Adventures of Winnie the Pooh
- Monsters Inc Laugh Floor (or whatever its name is)
EPCOT
- Journey Into Imagination with Figment
- Honey, I Shrunk the Audience!
- Judi Dench's patronizing narration for Spaceship Earth
- Bruce Broughton's Spaceship Earth muzak
- The computer screen ending of Spaceship Earth that is emblematic of how mediated our experience of the world has become
DISNEY HOLLYWOOD STUDIOS
- The Sorcerer's Hat (a.k.a. Terrible aesthetic crime and Disney's obvious attempt to sabotage The Great Movie Ride)
- Sounds Dangerous (a.k.a. I can't believe this is still open)
- Voyage of the Little Mermaid
- Beauty and the Beast - Live on Stage
- Indiana Jones Epic Stunt Spectacular
- The Magic of Disney Animation (a caricature of its former self)
- Lights, Motors, Action! Extreme Stunt Show
ANIMAL KINGDOM
- Chester and Hester's Dino-Rama
By the way, these aren't necessarily attractions I think are bad. These are just the ones I don't feel emotionally attached to.