BrerFrog hit it pretty well.... Horizons and WoM have large and sizable fan bases because they're gone. UoE doesn't because it's still there. End of story.
Look, I loved Horizons and WoM, some of my best childhood WDW memories are from those rides (I considered Horizons my single favorite attraction as a kid), but I also remember UoE fondly (those were some amazing AA scenes in the mid-80s!), and had it vanished in the night instead of getting an Ellen layover, I'd be willing to bet the tiny vocal minority would be skewering its replacement and shedding tears over it as well.... likewise, if Horizons or WoM had stayed, you'd hear complaints about that stale corner of the park no one ever goes to (like UoE now).
As in celebrity, the best thing you can do for your career is, unfortunately, to die young. Horizons and WoM did, so they have the cult following, reputation, and the villagers in a tizzy as to their demise... their untimely end lets us forget that they were failing empty walk-on attractions at the end of their lifespan (as, say, we forget about fat Elvis playing to half empty theaters in Vegas and being woefully "uncool"). UoE, meanwhile, is the old rock star hanging on playing in casinos and art festivals who has become a caricature of himself.... and so it goes.