I'm afraid that I have to disagree on a couple of points there. EPCOT Ctr. had a very unified idea of what was supposed to be. Walt's original idea had absolutely nothing to do with the EPCOT Ctr. that was opened in 1982. Walt's EPCOT was an actual planned city. Not a theme park but a working community. My strong opinion is that it was an awfully good thing that Mr. Disney didn't live long enough to actually make that a reality. It would have killed, bankrupt and destroyed the Disney Company. It was an idea that was so communal that it was against all the stuff that Americans called sacred. The only reason why MK was even part of it was because Walt was made to realize that in order to have financial backing he need to have a reason for people to go to the location. MK would be that tool.
Neither EPCOT or Disney MGM were ill conceived as far as purpose was concerned. However, many things that look good on paper, do not always pan out. With Epcot, Disney misjudged on two counts. One was that many people were not impressed with the Edutainment aspect of the park. Many felt that they were being forced to attend school while on vacation. Second, at the time that both were built technology was moving at a much slower pace then it was by the 90's. Just like Tomorrowland, it didn't take a scientist to realize that it was impossible to guess what was to come in the future. It was moving so fast that even if they could make a guess, by the time they got it into place, it would have been obsolete. Disney/MGM would have been logical on paper. They were a studio, all that had to do was divide up the workload between California and Florida, but, that proved to be expensive and hard to manage... so it was just left to decide it's own destiny.
DAK is a beautiful park, but, it is a dull park. Without EE it could be a rest home. Because of the needed foliage to create the theme, it is air restricted and without a doubt the hottest park in all of WDW. The constant responsibility to maintain the animals in a safe and humane way, is very costly and I really doubt that it pulls it's own weight, profit wise. So if anyone were to ask me I would have to say that the mistake, if there is one, would be in opening DAK. After all these years it still hasn't grown a large enough audience to call it a success. It was a great idea, but unneeded and has drawn millions of dollars away from the other parks basically since it opened. If one doesn't believe it, just think about what would happen, right now if they decided to shut down EE to fix Disco Yeti. It would almost be a ghost town. Everything other then EE is a do once attraction. Do them once and there is no need to repeat.