I'm getting really tired of people using this reasoning of "Walt said Disneyland/World would never be complete, therefore, every change is a good/necessary one!" Also hi there everyone, I've mostly lurked around these sites for years so I suppose I should give my take on what EPCOT "should" be.
Truthfully I think the whole idea of EPCOT as a "24/7 World's Fair" has a lot of potential and makes it stand out as a unique theme park, and in some ways a necessary one. If Magic Kingdom is a park about how awesome fantasy and make believe is, EPCOT (ideally) should be about the ways our own world is awesome and could be even more awesome. It should show us the innovations made by mankind over the years, and showing the incredible things that can be done with newer innovations for the worlds of utility and art. It should be an outright stubbornly optimistic rally cry that our "spaceship Earth" CAN be a wonderful place. And yet, I think Disney ended up doubting themselves because they kept missing the mark with the balance between education and, well, imagination.
People want to ride alongside dinosaurs and see the wonders of the world in action, what they DON'T want to do is sit in a theater for 30 minutes and be lectured at. Rides like Horizons, Journey Into Imagination, and even the entire Wonders of Life pavilion got it right, but others like UoE and Living with the Land were a snoozefest for the average guest most of the time. Then, Disney eventually threw their hands in the air and said "screw it, I guess reality is always too boring and upsetting!" and eventually that's how you got your "Seas with Nemo and Friends" and "Frozen Ever After" rides (Well, I'm sure the brand recognition also helps attract guests and gets those ticket sales up). I'm sure we'll eventually get even better rides for EPCOT over the years, but I'll always be a little upset that they turned "A look into how our own world is magical" to "Tomorrowland 2: Nova Corps Boogaloo."