One thing that surprises me, is that the Great Movie Ride was the only attraction, besides meet and greets to pay tribute to Mary Poppins. It could be argued that Mary Poppins was one of the top 5 Disney films of all-time. Then when you figure that they are actually doing a sequel to Mary, starring Emily Blunt, I find the rush to replace it all the more dubious. Whenther this new ride is anything or not, and it may very well be, is still debatable, but GMR was the Spaceship Earth of the Studios. The loss of the Wizard of Oz scene, and various other aspects makes this a harder pill to swallow. In the movie montage at the end, they even pay tribute to Lady and the Tramp and the Incredibles.
An interesting idea, though I haven't seen it mentioned, was if they could somehow combine the two. For example, remove one of the less popular scenes in the movie ride, and using the new technology for the ride, do Sorcerer's Apprentice from Fantasia. A ride that some deemed outdated would be completely cutting edge, but would still keep classical elements. It'd even have one of the iconic versions of Mickey. After all, cartoons are movies. The Great Movie Ride was themed to be riding through the movies ala Munchkinland, the Alien spaceship (Nostrama I think?), the Well of Souls, the Wild West, the Underworld. If you just added the Mickey room, you'd be in the heart of a cartoon. Why not simply add the Mickey room and blow the roof off the thing? Mickey would be the headliner, and draw, but the educational value and nostalgia would still be present.