1. The Exterior - I don't think this needs explaining because it's obvious.
2. The Interior - Compare the interior queue of Snow White to that of the one in Monsters. The experience is cohesive inside and outside when it seems they ran out of money for the queue at DCA and made no attempt to hide it.
3. You are comparing an attraction that was made 40-50 years ago to a modern one? The Fantasyland attractions I believe are artistically superior in every way. They may not have modern technologies but they make up for it in other areas just like Jungle Cruise does, it has charm. The very idea you would even contemplate comparing these old attractions to the modern one says a lot about the quality of Monsters. There should be no comparison and Monsters should win hands down but it doesn't by a long shot and that's the problem.
4. The attractions in Fantasyland are compact in nature giving an in your face feeling. The cars are smaller, the actual paths are narrower, and the cars are faster. In Monsters you have to share a vehicle with others and the pathways are too wide for such little animation. The only way for it to make up for this is to have full animated Animatronics, something to wow the guests. The scene with the helicopter and the doors is a perfect example of what they need more of on that attraction.
5. Unique experiences - Can you honestly deny that flying in a boat is more thrilling than a ugly taxi cab?
6. Darker - Every single Fantasyland attraction uses this very old technique to create a cool factor not present very often on Monsters. The only rooms that manage to do this in some fashion is the tunnel entrance and the door room.
7. You say that comparing E-Tickets to Monsters isn't fair however, I can compare the detailing of Fantasyland attractions to that of the E-tickets. The quality of the build may not be nearly the same (Cardboard) but the care of detailing is the same (Paintings).
8. Monsters Inc. the movie isn't nearly on the same level as Peter Pan or any of the classics.