I can't speak on all the assorted observations you made because I haven't been there since 2019 and probably will never be going again but I do have an opinion about the part of your post that I bolded. You are correct, our perception as a child is far different than that of when we are adults. The world is far more harsh in adult life and that carries over into everything. I never got there as a child. I was 35 at my first trip. For me there was a degree of Magic, but never the type that most people describe. For me the place was bright, fun and relaxing. It was a great experience for me in that, as Walt wished, we were able to do things as a family, laugh and have fun. But the mystical Magic as it has come to be known didn't really fully connect. I love the experience for what it was, not what I thought it was or should be. I enjoyed and looked excitedly forward to all 48 visits over 40 years and still would if I were physically and financially still able to do so. However, I never did it because it was magic, it was because it was entertaining and technologically great. Although I loved many of the original attractions, that keeping up with technology aspect is what made me enjoy the new and more advanced shows and displays. That's why I loved the original EPCOT and even though I miss the old attractions, I have continued to be impressed with what was change or created later.
I was never able to "immerse", I was only able to enjoy it for what it was, flaws and all.