> I don't think "class mobility" is a thing that we have to have. I don't think its a problem that needs fixing.
Really? If there were zero class mobility, that would mean that no matter how hard someone works, no matter how good their business ideas are, they'll never become more wealthy than their parents were when they were born (at least, compared to someone who sat around doing nothing). And it would mean that no matter how inefficiently or stupidly a rich person blows their money, they'll never become less wealthy than they already are. Bloodline would become a better predictor or wealth and status than luck, charisma, investment opportunities, or hard work.
Even if we lived in a world where even there poorest of the poor were provided for, I wouldn't be okay with zero class mobility. It would basically be acceptance of inherited birthright privilege.