Demand more what? Just as a thought experiment, I think the California Screamin' coaster was very popular when it was just California Screamin'. Plenty of people bought California Screamin' merchandise. Now that it is Incredicoaster, it makes more than California Screamin' because....what? Is it proven that more people buy Incredicoaster merchandise than they did when it was just California Screamin'? Is it proven that people are inspired to watch Incredibles stuff after riding the Incredicoaster? How is that measured? In Blu-rays? Disney+ subscriptions? Has viewership of Incredibles property gone up since the advent of the Incredicoaster? Have people indicated that they watched the Incredibles because of the Incredicoaster?
Let's go the other way. People watch the Incredibles and want to ride an Incredibles ride. Seems fair enough. So you build a $100 million dollar Incredibles ride. But just because it has the Incredibles on it, does that mean more people want to come to a park? If you built a $100 million non-IP attraction, are we sure the money earned is greater if it is a $100 million Incredibles attraction? How would you know? Seems like you would have to build two $100 million dollar attractions in separate parks, and then track over time to see who is coming to which park more, and then tie the reason for entering that park to specifically that attraction.
I would guess that, if both attractions are at similar quality levels and similar merchandising and dining potential, that only initially will the IP attraction get a boost, and only if it is some sort of really beloved IP (i.e. Harry Potter) with strong theme park potential (not Big Hero Six, lol). But over time, the non-IP property will become its own draw, and bring in just about the same amount (i.e. Knott's Ghost Town Alive).