You're not far off.
Burning Man is like Coachella, SxSW, and San Francisco, itself.
It used to be cool, and interesting, and counter-culture.
But then it got overrun by tech people and grifters and assorted wannabes who think they can buy their way to coolness, when that's something that can only come from within.
https://journal.burningman.org/2016/10/philosophical-center/...
No, it's not inevitable. Burning Man is just making excuses for selling out.
Look at how high school kids dress these days. The cool kids today style themselves much the same way as the cool kids did back in the 2000's, the 1980's, the 1950's, and to some extent even back to the 1930's.
Blue jeans and white t-shirts. Concert shirts. Doc Martins. The infamous "little black dress." Dorm room posters and pin-ups. Even hair styles. Some things are "classic" and always cool. Burning Man isn't one of them.
Personally I think the world is a little better off by it going somewhat mainstream.