In a lot of ways it’s a problem of being too inspired and too passionate. Being a theme park designer is now something to which people aspire. You can get a degree from known universities in themed entertainment design. So the inspiration in theme parks, and especially Disney’s parks, is no longer the real world but theme parks themselves.
Go look at Joe Rhode’s Instagram account and it’s about people, places, art and history. His fascination is with the real and he imitates that in his work. Herb Ryman was known for his traveling to paint. As was Marc Davis. Hench vigorously studied philosophy and design theory. When Walt brought in Nelbert Chouinard to teach the animators she didn’t have them copying animation but real life subject. When it came time to make Bambi they brought in real deer to study (Andreas Deja recently posted on his blog reactions to The Lion King from some of the old guard and Marc Davis complained the lions looked to cartoony). The lands of the parks were built very much as real places, or at least the illusion of real places whereas now they’re built as fake places. New Fantasyland 1983 drew more inspiration from European villages than the films that inspire so much of the land’s content but Nee Fantasyland 2012 is very much drawn from the movies first and foremost. The parks have moved from copies to copies of copies.
This has also combined with increasing specialization. The visual elements of theme have become something distinct, an application applied on top of a box. Disciplines have become more layered instead of melded together and intertwined.