I think the issue is when you own a part of the park some think the renters are riff-raff. It would be just like living in a subdivision and you have a renter next door. Some folks would watch them like a hawk for a chance to see them doing anything wrong.
I definitely wouldn't categorize all ownership parks like this. Again, a few folks make it difficult for others.
Ourselves, our first choice is always a public park - national park, state parks, national forests, etc. We like our space and nature around us. We don't need all the 'glitz'. Everyone is different.
OP: When you retire, why would you already be thinking of buying into one of those places? Wouldn't you like to travel and see our beautiful country?