It's a surprisingly complicated issues for something as simple as a theme park with all the layers of nostalgia and the agendas that impede an honest dialogue.
The best part is if you Google back into the early days of the internet and some of the newsgroups back then you can find folks complaining about the decline starting in the early 90s (you might even recognize some usernames!). I'm sure if the internet were more accessible in the 80s the decline would have started then and in the 70s we would all be complaining about the copycat DL coming to Orlando.