Sounds like the OP has been doing some typical parental worrying, but has been reassured by many of the stories here. I agree with all those who have said as long as kid is able to support himself at a level he’s comfortable with, and likes–or better yet loves–his job, all is well. And he’s young yet, so definite possibilities for financial improvement.
In my experience I see some truth to the high SES families’ worries about downward financial mobility. Where I live, to match the UMC lifestyle they may have grown up in requires two six figure incomes (or one amazing one). This dictates not only the choice of career but also the choice of spouse.
Among my own friend groups’ kids, here and other high COL areas, we have accepted that the kids will likely relocate to less expensive areas, and indeed the majority have. Those recently graduated from college are living typical 20s lifestyles, building careers and sharing apartments. Those a bit older have been able to buy houses and are raising families in comfort.
And just want to acknowledge those with adult kids unable to work/support themselves due to physical or mental illness (fortunately not an issue in my own family, but I do have close friends in that position). There’s a tacit assumption that we’re talking about able-bodied kids, but sometimes life has other plans.