If growth stalls but expectations of what "success" looks like in life remain the same then inevitably the more rational amongst them will look and see that just achieving a "normal" life seems incredibly difficult.
I'm not saying it's not serious, it's also not particularly special to PRC. Like the few tanping kids I hear about IRL in PRC are like your typical western kids with comfortably wealthy boomer parents who can afford to fuck around because they got safety net/inheritance down the line. Everyone else grinding while joking about tanping, like antiwork folks in the west bitch about their conditions, but eat continue to eat shit all the same.
and the ability to be extremely vocal about it -- which could get you sent to jail or otherwise ruin your life via social credit scores.
point is, the kids in China have it notably rough.
Emerging PRC analogues to NEETs/Hikikomori are "full time kids". TLDR is high savings rate and culture = kids live with parents and do bumfuck while looking for jobs they think are their level. Some will settle for employment beneath them, some will live off their parents dime if their parents can support it. Cause is PRC went from single digit to 60% tertiary rate in last 20 years, there's too much talent/competition last few years as graduating classes got larger and larger but not enough jobs uni kids want.