IMHO, there's a distinct gap between nudist venues which totally deny any connection with nudity and sex, and those that acknowledge that some people like sex and are happy to have it with other like-minded people should the occasion arise. They have dances at most of the resorts I've been to, and while some people like to dance for the hell of it, most of the rest of us appreciate the flirtation that sometimes goes on. As I learned in college, "Dancing is a vertical expression of a horizontal desire." Or it can be. And I don't see anything wrong with that, any more than I'd come down hard against it in a "textile" setting.
But in either a nude or clothed setting, it's not about public sex. If people want to indulge in it, they should find someplace more private to do it as a basic gesture of respect for the feelings of the rest of us.
I do agree with the premise of the topic that younger people are open to being naked with other young people they know and trust, but they're not eager to be nude for nudity's sake. They'll shuck their clothes when it's hot-tub time or skinny-dipping, but they don't go out of their way to be nude to strangers, particularly older people. They don't see the point. Neither do I, really.