How many of those things would have been a good idea to base an attraction on?
Maybe it would have seemed like a good idea at the time because of it's immense popularity, but in hind sight it would be extremely dating and embarrassing at this point.
For me there are three things that are truly objectionable about IP.
1. Instantly date the attraction to the point in time the movie(s) were popular.
2. Instantly polarizing to people who have no interest in the IPs themselves. No matter how popular a movie is, the majority of people will have not seen the movie therefore won't have much desire to ever travel to see an attraction based off of it. In my opinion, you shouldn't really need to see a movie before you'll completely appreciate or care about an attraction.
3. Finally, the fact that they are a cheap, marketable replacement for anything unique, creative, or park specific. Think of how many park specific characters/stories they could create and hype. I'm talking things like Harold from the Matterhorn, Hatbox Ghost etc. They could create characters and stories you can only get at the parks and market the hell out of them. Create merchandise you can only buy at the parks. Disneyland would be it's own unique, creative experience full of things to discover instead of just reliving a movie you saw 15 years ago and sort of remember liking at the time.