Problem is that EPCOT's theme was always problematic from the start.
What is an EPCOT? What is the theme of an EPCOT?
The word is just an acronym of a project that never happened.
It's clear it was meant to mimic a world's fair with all the cultural and technological pavilions. But it never advertised itself as World's-Fair-like.
World Showcase succeeded in that it was a realm of cultural showcases. (Though certainly, the national pavilions were not "communities of tomorrow" -- ironically, they focused on the past.)
Future World.. was a mixed bag for the theme of *FUTURE!* The technological showcases, as good as they were, became outdated and corporate sponsors refused to pony up the dough to update the pavilions. So, they became Disney's financial black hole.
Without sponsors to sponsor, Disney was the sponsor, which naturally led to inclusion of Disney IP and the 'Disneyfication' of EPCOT. (Even though EPCOT was indeed Dinseyfied by being a creation of Disney to being with.) And then came the modern doubling down on IP (which isn't just a Disney thing... almost all theme parks rely heavily on IP [cf. Epic Universe].)
Beside becoming outdated, some of Future Worlds offerings weren't really connected to *the future.*
SSE was a *history* of communication. Figment isn't the Future. Soarin' isn't the Future. Test Track featured contemporary cars, not the future of car tech. (Ironically and sadly, both Future World and Speedway feature gas combustion cars... which are now becoming a sign of bygone times... just a reminder of how tech becomes outdated quickly.) An aquarium isn't futuristic even with a veneer of pretending we descended to an underwater lab... it's still just an aquarium. A good one, but not the aquarium *of the future!*
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Making Epcot like a World's Fair is to invite not having a *theme* except the theme of a World's Fair. World's Fairs don't have a theme except... World's Fair. It's a world celebration. In many ways, the year-round festivals totally fit in that regard.
Out of place would be IPs that have nothing to do with a world celebration. Harmonious tried to tie in the world with it's multi-cultural IPs and use of world languages, and did so poorly. I believe it could be done well.
Epcot's theme is indeed the world's fair thing! I don't think it needed to be advertised like that in such literal terms, but it's clear it's an exposition dedicated to international culture, new technology, new industry, new transport and human achievements, all that was indeed promoted. A commentator covering the opening observed that this was somewhere where you would not see any Disney characters. Something completely different from every other cookie-cutter theme park, it was always seen that way, it was never hidden away. You could describe the expos and world fairs as theme parks in that regard. The name/acronym EPCOT is a label, in honour of the original city project which was to have been built around all those aspects. EPCOT Center can be seen as the "visitor centre" for EPCOT, the project, a place where the concepts are to be demonstrated. It's the visitor Center for EPCOT. It makes perfect sense in its original context.
The closest I can get to Epcot in the amusement park world today I think is Futuroscope in France. A friend of mine commented recently on visiting for the first time "What looks like Epcot but has operations like Six Flags?"!
However, we can probably call Epcot a flawed masterpiece. Even on opening, there were a few ideas that never made it, that would have made more sense in the context of "The Future". The Seas and Space pavilions were meant to project how we could eventually live in those environments. However, Horizons summarised those ideas instead. Sometimes in a more whimsical Jules Verne type of way but then ending with serious ideas and plenty of food for thought and contemplation. World of Motion also showed the possiblities of future transport. Universe of Energy showed the future of energy generation. All those pavilions also started off in the history, yes, but that's how to tell a good story! They used to do it well in those days. Spaceship Earth also shows us concepts of the future and again starts off in our past. It's all quite consistent in the way Future World worked and also consistent with the mission statement.
Of course projecting the future will become out of date, hence the need to keep on top of this and make sure the pavilions are refurbed in a timely manner. Unfortunately, refurbing has turned out to mean demolishing and turning into something else, rather than putting the effort into keeping it relevant. It needs to evolve and change, "it's not a musuem", but that doesn't mean it inevitably has to evolve into something else or change for the worse. Neglect and indifference cause the problems. You bring up the ideal example in Speedway! But if we followed the same trajectory, then instead of Speedway being updated with a more appropriate mode of transport, it would be demolished and replaced with an attraction based on a Disney princess, with some loose connection being made to the concept of Tomorrowland to try and make it fit.
World Showcase also shows us a lot of history, yes, because that's crucial to understanding how these nations and cultures developed, in a similar way to the Future World pavilions. But they're also rooted firmly in the present, with contemporary foods, entertainment and goods. Remember though that Epcot, the park, was a product of the imagineers working out how to proceed with it and discussing two separate angles of Walt's visions. they couldn't decide which way to go, so they took the two ideas and joined them, World Showcase isn't about "the Future". It's literally a showcase of nations of the world.
Figment isn't "the future", no. But let's go back to its proper name, Journey into Imagination. This was all about the human condition, how we use our imagination to create things, literally. Works of art and how we use science and develop technology. Human achievements, you see, and possibilties for the future. And what could be more ideal, it had built-in characters! The hit combo of Dreamfinder and Figment. They weren't imported from elsewhere, from a movie that they starred in. Imagination was their story, they told it, and it was our story too. The journey through imagination was scary sometimes, but that's OK. Unfortunately, the point was missed when there was an outcry when the ride was butchered and the characters disappeared. People who remembered the original attraction weren't necesarily mourning Figment exclusively, it was the whole thing. The whole package, Dreamfinder included. It really was a stunning attraction and floored many people, myself included. So the slated new Figment meet 'n greet isn't necessarily going to satisfy Epcot fans, only those who do like cuddly characters to meet. It would be amazing if Dreamfinder also appeared in the meet 'n greet, but since he has been purged from the attraction I don't think that's likely.
Soarin isn't "the future", but remember this is a product of nu-Epcot, and is arguably a relatively decent fit for its pavilion, as are Mission Space and Test Track. Now let's go back and have a think about Frozen Ever After and The Seas With Nemo and Friends...
But of course, it's changing, the subject of this thread. What is it supposed to be now. I think Hollywood Studios has the same problem. Its name now longer fits, nor its mission statement (the Hollywood that never was but always will be?). Used to be true for its original incarnation, but no longer.