The IP is perfectly suited to theme parks in a way that no other IP really is. An escapist fantasy with incredibly iconic and realizable locations, characters, activities. A very major part of that fantasy is the appeal of going to a really cool and exclusive(!) shopping mall and buying a bunch of fun toys. Of going to a store and having a unique bespoke experience purchasing a wand with the shopkeeper. Of sitting on a train and buying and eating a ton of fun and weird candies. Within the world of the movies and books, and inside the land, if you see someone using a wand casting magic, or wearing nice Hogwarts robes, or holding their expensive Quidditch brooms, you are urged to think of that as a cool thing and to want to be like them.
At a theme park, you buy stuff, you ride on moving vehicles, you eat nice and fun themed foods, you interact with themed entertainers. The overlap with the appeal of the Harry Potter fantasy is essentially 1:1, and its' "immersive" qualities set a standard that quite literally no other IP could match. It started that trend of "immersive" single-IP lands, even though the concept had existed way before Potter. All of IoA was essentially trying for that goal, but it took Potter for it to become the template moving forward. Potter was the industry turning point.
You don't see Luke Skywalker or Han Solo shopping for Droid parts. The heavy push for merchandise with Pandora feels weird and unappealing because Avatar isn't a movie about adopting a Banshee or eating alien burgers at a food hall. You don't jump on Goomba's or platform your way through Mario Land, you use your phone app and you take the stairs. They can still be fun and cool, but it doesn't tap into something the way that HP did.
You can try selling as many Lefou's Brews or Blue Milks as you'd like. They're all copying Butterbeer. The Power-Up Bands (and likely incoming Pokédex/Balls) will be very successful, in largely similar ways to the Wand experiences. You can make superior rides like Rise or Unchained, but it doesn't matter. It's been done before. You can only make that impact once. It was a perfect storm.