EPCOT Center is not "Disney." Many Disneys theme park fans have no interest in themed entertainment that lacks a connection to something already known as Disney.
I have a problem with the foundation of this statement.
First, lets use Frozen as an example. Prior to Disney creating Frozen, the characters did not exist, and therefore had no connection to anything already known as Disney. Once Disney created Frozen, is that when it suddenly became more Disney than attractions that have already been in a Disney theme park for decades?
From another point of view, Pirates of the Caribbean had absolutely no connection to a Disney when the ride first opened in Disneyland. Was it therefore unpopular and avoided by the park guests? Same for Haunted Mansion, Big Thunder Mountain, Soarin', Test Track, Space Mountain, Space Ship Earth, The Land, the original Journey into Imagination, Kilimanjaro Safari, Expedition Everest, and tons of others. None of those had themes that were connected to anything already known as Disney. Heck, Tower of Terror isn't even a "Disney" property, but is incredibly popular. But, once they appeared in our theme parks, they became Disney. What do they all have in common? They are high quality attractions, regardless of whether or not they were themed to something that already existed in a Disney property.
EPCOT isn't any more or less Disney than any of their properties. By your argument, the Maelstrom ride in Norway at EPCOT has been "Disney" for a lot longer than Frozen has been "Disney."
EPCOT is the third most visited theme park in the United States, and sixth in the world. I'm not sure I would say that Disney theme park fans have no interest in going to EPCOT. By the numbers, I would say that EPCOT does incredibly well with guests.
If you instead mean that guests have no interest in themed entertainment that doesn't connect one of Disney's animated features...well, that is a different conversation, but I make the same argument.