The foreseeable future for theme parks as we've seen is more intense and immersive lands and attractions. While original content (wholly born within the theme park) can be immersive, its not always going to be a success. So that is where the business side comes in, using IP that you know will at least draw in the crowds. Its a marriage of using the IP for familiarity and the immersiveness of the new offerings that make them a success.
Your example of Car Land is a perfect one. While it may appeal to a certain section of the public who are into the car culture it may not appeal to the larger public. And that is again where the business come in. What is going to bring more of the public into an area of the park. An area about the car culture of California or Radiator Springs? I heard plenty of people while standing in line for Racers say things like, "Hey I don't like the Cars movies, but I love how immersive it is and feels like you are in the actual movie".
Also the Cars universe is not just Radiator Springs. Its also Planes and that franchise. While it didn't do as well as Cars it is a creative direction they can go and still be within the Cars universe.
And as we've seen they are moving away from the idea of DCA being about California the location as the theme. Which makes sense, because they were locked into a concept that was way too limiting in my opinion. Now they can bring worlds into DCA that allow for greater creativity because you don't have to tie it back to California the location.
You just reiterated my point that IP-based lands and attractions are safer choices.
Disneyland has survived six decades without IP-based lands. Would you say people don't like Disneyland because the lands aren't based on single IPs? No, right? I wouldn't call Adventureland, New Orleans Square, Frontierland, etc. unsuccessful. I'm not sure where you're getting this idea that people don't like original concepts. Look at Pirates, Mansion, Thunder Mountain, etc. Are these attractions not considered classics? Do they not draw in crowds?
You can't say a land based on California car culture wouldn't have brought in crowds without something to back it up. You THINK it wouldn't have drawn in crowds, which I don't believe would have been the case at all. Disneylanders have proven again and again that if you throw anything at them, they'll show up. I think of the the Golden Horseshoe tribute Disneyland put on some years ago. That was incredibly popular and it wasn't tied to an IP. The Dixie event the park put on for annual passholders also comes to mind. Car Land didn't even have a chance to come to fruition, and I fear any other land that isn't based on an IP will have the same fate.
Planes is still a single IP. And let's be honest, the chances of us seeing anything from Planes in Cars Land are probably slim to none.
It doesn't make sense at all, especially since Disney recently went through a five-year process to incorporate more California into the park, fantasized or not. How is California limiting, but Cars isn't? California is arguably the most diverse state in the Union, with rich history. The park hasn't touched multiple aspects of California. I'm curious, did you grow up in California? If so, remember all of that California history we learned in elementary school? California opens itself up for a VAST array of ideas to pull from, but guests tend to accept mediocrity nowadays, and now a land themed to MARVEL will be going into CALIFORNIA Adventure. But who cares? Marvel is cool and will make the company plenty of money. What then is the point of the theme park?