>Parks are all gated by HOAs

The near universal proliferation of owner's associations and management groups and whatnot is something you can lay square at the feet of the environmentalists.

Some big commercial developer developing a subdivision in 1970 would've allocated a couple lots as a park owned by the city or town. I live in a neighborhood like this.

Now those empty lots and the exact layout of plantings on them are a key part of the green space on the site plan that makes the bullshit spreadsheet math that is required for your stormwater or environmental math to pass requirements. And and some legal entity has to be responsible for that in perpetuity. Enter the HOA. And of course then they make all this stuff private because they can market the units in the development better that way.