Or they'll be fine, marry loving partners, get into doing something lax like flipping cars or real estate, spend more than they probably should on entertainment

Or they'll be fine, marry loving partners, get into doing something lax like flipping cars or real estate, spend more than they probably should on entertainment, have a kid or two, pay off their $100k home by retirement age, and live like most of the bottom 40% of the US. Not everywhere has money. I'm from a place where mortgages (with PMI) plus property tax are under $600/mo, families mostly own one vehicle (a van or truck), and people outside of regular blue collar either work six months out of the year trucking, at one of two local corporate offices, or hold multiple jobs part time (30-32 hours per so they don't ever get benefits). That's how a lot of America lives, and that's who Medicare4All, free higher ed, and federal funding for K12 helps the most, which would do a lot to build and reinforce our lower middle class.