I'll agree with this. The one thing I will say is that there has never been more fragmentation than now. There are so many things vying for people's attention today. Even 10 years ago people going to wdw were more of a captive audience. Today you have to compete with every person having a computer in their pocket. It's like Gone with the Wind. There is no way it is the success today that it was when released. People had no choice but to see it dozens of times because there wasn't anything else fighting for their attention. So right or wrong Disney has to move away from what worked in the past because the vast majority of their customers have.
While there were less options to go to in Orlando in the 1980's, there were also vastly fewer people making the trip. From the best attendance stats I can drum up through Google, it appears that Epcot maintained an attendance within 1.5-2 million of the yearly Magic Kingdom numbers through about 1996 (even with the new Disney-MGM Studios opening in 1989). Then as growth of the market and growth of park tourists has come through with the Universal parks, etc, Magic Kingdom has grown to exceed 20 million in yearly attendance while Epcot has more or less stagnated with the same 10-12 million range since the 1980's (with some dips below, particularly post-9/11).
I think Gone with the Wind worked in its day because it was a grand spectacle compared to most other options of the time and people could see effects and imagery that they could not get anywhere else (the Avatar of its day). Magic Kingdom has that grand immersion that captures people on a scale they cannot get elsewhere. Animal Kingdom has done a good job of creating a grand experience with their vast and open animal exhibits, to their well themed lands, that also manages to pack a good bit of educational info into the park (even the Dinosaur queue has some educational elements). Animal Kingdom has recently overtaken Epcot in attendance as a result. When Hollywood Studios opens the Star Wars land, it will have a big spectacle (that also helps it tighten up the park's overall movie and tv theme a little, even if not really a studio anymore) and will more than likely pass Epcot in attendance too, relegating it to the fourth gate status.
Epcot had this until sometime not long after the original sponsorship agreements ran out and the pavilions were left without attention or were cheapened (looking at you Imagination pavilion). Epcot has big, impressive buildings and spaces where impressive attractions could be, but overall they didn't update or expand, they regressed over time and stagnated (they did add Soarin, Test Track, Mission:Space, and now GotG, but those replaced rather than added and each followed a period where the park took extended time essentially ignoring the space before anything happened to it). Guests notice "empty" and it can shape the overall image of the park even if there are still some compelling elements nearby (think about how MK would look if in the late-1990's they just shut down Thunder Mountain, Crystal Palace, Haunted Mansion, and Hall of Presidents and didn't replace the space with anything for a decade). Guests want something to capture their attention, it doesn't have to be IP, it just has to be something they couldn't otherwise find in their local shopping center. When they walk in to Epcot now, you do see the impressive Spaceship Earth, but beyond that, the early impression of the main avenue of the park is encountering the shell of Communicore/Innoventions with basically just shopping, character meet and greets, and empty space where something cool used to be. If they turn left, they see the shell of UofE then the empty WoL building before getting to something they can actually experience. When you walk around, you go by the empty Odyssey building, the weakened Imagination pavilion (with its closed upstairs attraction space, cheapened ride, and activities that never work right in the post-show Imageworks), The Land has a big empty space where Circle of Life was, The Seas has stripped much of the theming and show that it formerly had as well (taking out the hydolators, scientific queue displays, pre-show).
My guess is that if, instead of replacing many of the above areas with meet and greets or nothing, they had either freshened the old rides or put in real attractions, Epcot would have had a better chance at maintaining its own identity and would not have lagged behind Magic Kingdom's attendance growth nearly as much as it has.
