I don't think its just about the public, I think that IPs solve a pretty logistical issue: trying to tell a story with developed characters when you have pretty much no time to do it. Universal (while yes, they do use IPs pretty heavily also) makes the mistake of obsessing over plot, using pre-ride videos, obsessively using screens, etc. to the point that we're just pretty much just watching a cheesy 10 minute movie. If you use an IP correctly, the riders know the characters and know what the plot is all about, and when you get on the ride, you can just enjoy the ride and not worry so much about character development and an intricate plot.lol, quite a number of places actually nowadays.. That's why I think Disney is actually smart to give it's public what it wants, even if it is IP heavy.
years ago, Disney may have been the best game in town for family vacations. Now, many, many vendors have stepped up their game.
Now of course it's hard to compare apples to apples because of the size of Disney but we've been to two all inclusives in Playa del Carmen where the attention to detail was insane.
I think that to have amusement parks rides with plots, you'd have to over time have rides that built off each other, and slowly add more and more character development and more twists to the story. Hasn't really been attempted much (I guess maybe Pirates of the Caribbean may been a start? Or maybe Figment?) but you'd have to do something like that. Might be a cool, ambitious thing to do though. You have to admit, Space Mountain pretty much never had a real plot. It was just about the visuals, sounds, and experience.