And who said Epcot Center 1983 - 1990s was not popular?
(Warning- this post is a ramble, and is mostly based off personal experience which makes it irrelevant. Feel free to skip it. It's late and loud snow plows are keeping me up.)
What Disney park isn't popular? A poor performing Disney park still lands in the top 25 worldwide.
I mean, DHS experienced only a minor dip in 2017 with half the park shuttered, no new offerings, and fresh competition from it's sister parks and beyond. Still very popular. But did it deserve to be?
I'd never argue against the numbers, but...
There was a palpable buzz when the 21st century arrived in 1981. My neighbors, classmates, people who weren't previously interested in visiting a Disney park, all were intrigued by this new and unique offering. I'm sure many have noticed people around you who have never mentioned interest in Disney or theme parks that seem to be buzzing about "Star Wars Land." I'd say it was like that, but on an even grander scale. My family went down the following summer, but by then most people I knew who'd expressed interest had already been. And as a child who read every article I could find on the park and watched every broadcast hyping it up, was shocked when most came back and all they could offer up was "it was OK." When pressed for more info I got comments on how spaced out everything was, how expensive everything was, and how little shade there was. I'd say it was akin to waiting fifteen years for a new Star Wars film, only to hear the first Phantom Menace reviews are "Meh."
We went and I had a blast regardless. And we went back every couple of years as many others did as Florida became firmly established as a reliably enjoyable family vacation. So, I don't think crowds waned much at all, but I think how those trips were spent may have changed. I think many things became one-and-dones. I think most exhibit areas, or basically all of Communicore became nothing more than a shelter from the heat or rain. While on our first trip where we popped into every single World Showcase store, we later skipped entire countries as they had little to offer a family that wasn't there to shop, and had our main meals outside the parks due to cost.
I think Epcot was incredibly ambitious, and deserves all the credit in the world for trying to be as different as possible from the Magic Kingdom. I can see now there were problems born out of that need to be different- so much of what Disney had learned about park design, flow, and visual cues, were abandoned to serve this new concept. Clearly they had a plan for how to adapt to the future, but it was a costly and flawed plan that relied too much on outside partnerships. Change came slowly and what came first didn't seem to be going in the right direction. For as heralded as it is now, I don't ever remember a line for Horizons or Living Seas that wasn't in the single digits. Oddly, I do remember long waits for Body Wars which is odd as everyone here seems to have hated it (yes capacity and hourly throughput are important factors, but they do little for perception of popularity.)
You know what's happened since and yet the park is still popular. I enjoy Soarin and Test Track, and actually love Mission Space. The park survived the asinine wand and continues to live even with the open wound that is the horrible Imagination abomination. The park is going to change a lot. It has already lost Martin's love. And it will still be popular. And to go back to my first point, they could probably do nothing and have an only slightly less "popular" park.