The thing is; from my standpoint, the majority of people I know who go to Orlando go for “Disney World!”, and even on my last trip to Orlando in 2019, the bulk of people in the airport were decked out in Mickey ears and full Disney apparel, looking like they were going with Disney as their sole purpose. The airlines and holiday companies also still very much emphasise Disney over the other parks in the area, which would suggest they are still far more popular by very nature.
While the likes of Star Wars Land will certainly appeal to a certain demographic, I’d wager that Disney could maintain broadly similar guest figures by not building anything at all for 5-10 years. As an example; if I’m remembering correctly, there was somewhat of a drought in major additions to the Florida resort between Expedition Everest in 2006 and New Fantasyland in 2014… yet the guest figures still grew, in spite of The Wizarding World of Harry Potter opening at Universal in that timeframe. I’m led to believe that Disneyland Paris also hasn’t been a hive of activity until fairly recently, but that resort maintains fairly steady guest figures (weren’t a lot of its financial problems caused by troubles during the early years rather than its modern day success?).
For a lot of people, I don’t think they visit Disney for its new attractions, I think they visit because it’s Disney. I don’t think any other park in the world has that kind of appeal, and that would naturally give Disney an advantage. Universal and some of Disney’s European competitors may be comparable in terms of quantity of things to do, but they lack Disney’s raw brand appeal, and in some people’s eyes, they’re nowhere near as good as Disney; I’ve even heard Universal described as “more comparable to Merlin than Disney”. The Disney parks, rightly or wrongly, have a special stigma attached to them in popular culture that will give them a fairly strong captive audience regardless of what they add or how they’re priced, which I don’t think you could say about any other theme park in the world.
And I say all that as someone who vastly prefers Universal to Disney; Islands of Adventure and Universal Studios Florida are two of my favourite worldwide theme parks, whereas no Disney park makes my top 5, so I’m hardly biased towards Disney.