You pretty much argue IPs aren’t necessary in a theme park. It’s not that you’ll object to IP, but where it occurred, you just think IPs should be rare than a normal part of a Disney theme park. It is so obvious that you forgot it one page back.
With this criteria, IPs should be considered only after original ideas are exhausted. We should also presume original ideas will always be successful since it happened, but we know of numerous failures with original ideas. The idea that Disneyland succeeds when their secondary theme parks hardly ever never succeeds without IP and this fact is always in the memory hole. But keep arguing this because that’s what you do.
Even more odd, secondary theme parks were always the argument to put IPs to keep Disneyland pristine. Of course, that’s why we argue Disneyland Resort should have a third park to have Marvel and Star Wars.
History had shown original ideas can be cheap and value designed. Then IPs came to the rescue because the cost for higher quality attractions is less of a risk to the corporate treasury. Plus a ready made backstory solves related theming questions.