The more "helicoptery" segments of society seem to be doing better, at least economically, than their more hands-off counterparts. There's a couple of possible explanations for this (including reverse-causation), but it seems at least plausible that there may be a material trade-off here, where the kind of self-denial that makes you miserable is also what gets you ahead. I haven't
personally found that that's the case - one of the big personal reasons I founded my company is to take a bet that I can succeed without being anything other than myself, both to prove it to myself and to everyone else - but I could very easily be wrong, especially because I really don't want it to be true.
The increasing competitiveness of careers and the ability to get "locked out" from early missteps seems like another possible causative factor. Setting aside for a moment to what extent it's actually true, it's certainly true that a lot of youth have a strong perception that missteps can screw them over for good separately from the ideas they're getting from parents.
There's less room to do stupid things in high school when your future depends (or at least, depends as far as you're concerned) on a four-year degree from a good school. To get into a good school, you need to rack up those AP credits. Better start in tenth grade, there's not enough hours in the day to get them all. And to get into those classes you'd better do well on that prep PSAT you took in eighth grade, so you should start prepping for it in seventh, and whoops look at the time you'd better start working hard there, hypothetical nine-year-old.
"Third spaces" vanishing is a physical manifestation of a broader phenomenon: the elimination of slack in a world that is optimizing it away in favor of, well, Slack.