It's the first generation that's going to be less wealthy than their parents. Perhaps that's also a factor.
In some ways I think this is due to our ongoing demographic shift. More and more of the US is getting old; old people typically have more assets than young people and need to rely on social security (which young people bear in taxes) and their investments to generate income. I think this is partly contributing to an asset bubble and definitely to the housing shortage (though there are other factors). I don't know if society has ever had a time where more households were not working but still drawing incomes.
But I think you're onto one of the core issues - an a much more personal lens. Many (including myself) compare our successes to that of our parents. They were married by 24. Finished Masters degrees by 26. Bought their first house by 30. I can't compare with that.
Regardless, I think as a problem it’s more mosaic, that to reduce it to any one cause is too reductive.
Of the (anecdata) pool I'm sampling from, the most anxious / depressed tended to be the most well-off. Personally, coming from the mixed background / lower-middle side, the non-traditional types seemed to fair better, such that I would anecdotally ascribe value to "blue collar suffering" as providing some measure of anti-fragility. But that's far into speculative territory.
In all honesty I'm fairly anxious, but I also can cope or at least mask as necessary. As I've previously expressed, I'm sure it's more a confluence of factors than any one item causing or precluding.