Animal Kingdom - Disney spent years convincing people that AK was "Nahtazu", when in reality that's all it opened as. Over the past 15 years they've tactfully kept Animal elements while totally veering into entertainment and rides to further the message that this was not just a zoo.
Hollywood Studios - Opened exclusively as a "you're behind the scenes" and "look how these things are done/filmed". Slowly morphed into a bad combination of "behind the scenes" and "within the scene" much like Universal. Hopefully by 2021 they will have completed the conversion to simply being a well themed movie/IP park with immersive worlds. Even Sunset Blvd fits that bill for the most part.
EPCOT - Conceived as a demented communist experiment, then morphed into a world's fair. And like actual worlds fairs (and Tomorrowland), it got stale quickly. The billion dollar "edutainment" park was hopelessly outdated only a few years after opening and families with small kids despised the place. Because Disney did not wish to continue the vicious cycle of being "new" every few years (again, like Tomorrowland), they finally put the concept out of its misery and brought in a key demographic with brands/IP's.
All three of these parks have undergone massive changes to the concept and execution of what the park was "supposed to be" when they opened. I get it, EPCOT was supposed to be one thing, and now it's not. Why is that so bad though? EPCOT has always been one of my favorite (if I'm honest with myself, it's my #1) park, and I'm far more angry at them allowing the place to become a dilapidated world's fair than seeing IP's brought in. They're not going to keep dumping money into attractions every decade in order to literally rebuild the entire park as stuff gets old or falls out of style. It's just smart business to find a new direction for EPCOT. Hopefully that direction involves less "seasonal events" for local drunks and more timeless attractions that people are clamoring for- even if that means IP and thrill rides.