How is this necessarily "better"? Highly subjective term, no?
I think what most people want is something that keeps with the original spirit of EPCOT without being stuck in the past with regards to technology and outlooks (e.g. no more acting like, say, solar power is some mind-boggling new thing), a park that's able to evolve as new information is learned, but also a park that isn't afraid to have some attractions that could be considered timeless the way that Pirates or Haunted Mansion are considered timeless (e.g. what the original Journey Into Imagination could have been). You have an entire resort that's "twice the size of Manhattan", which should open up opportunities for parks and attractions that are extremely unique, experiences and concepts you can't find anywhere else, but what it feels like we're watching at the moment is a movement toward homogenization, as if simple IP overlays can make up for a ride not having anything truly unique about it or a larger concept and presentation beyond "here are those characters you like". It isn't even as if IP overlays can't work, but previous and current work in this area simply hasn't been very encouraging to a lot of folks.
Beyond that, it isn't really as if the new IPs are going to draw in an enormous amount of fans; most of the fans who would be drawn in by a princess movie, by Marvel, by Star Wars, etc., are already there. Yes, you'd see long lines for awhile on a new attraction taking advantage of those overlays, but again, in a resort with so much space, why default on that, particularly when the law of diminishing returns sets in (e.g. what's happened over at The Seas, where waits are back down to next to nothing)? Why not do something nobody else is doing, and use the gift of space and size to craft experiences that can appeal to different segments of your prospective audience? You have plenty of space in the Magic Kingdom and the entirety of the soon to be updated DHS for a lot of that, so why is it necessary in EPCOT when the EPCOT concept itself can be a great selling point with the right kind of emphasis? If the answer is "because people want Potter", then I think it's kind of sad if the company is willing to play catch-up with Universal, and I think it's a bit short-sighted given that Harry Potter has a very unique fandom that lends itself to themed space that a lot of other properties don't necessarily have, so attempts to replicate it aren't often going to work that well.
If people were saying "bring back Horizons and keep all the cheesy 80s color pastiches and facial hair" with 100% earnestness, I'd agree that nostalgia was playing too big a role, but wanting to hold onto the founding concept of a park that had a lot of drawing power when it wasn't being neglected doesn't sound like some rose-tinted bifocal ranting to me.