Nobody is arguing there are no biases or suboptimal behaviours in the global economy, only that so far capitalism is the best system known for optimizing out those suboptimal behaviours. And that in particular, having governments try to short-circuit the process often make things worse rather than better.

"Tax brackets, medicaid, and public schools, to name a few. None of those are communism"

Tax brackets and medicaid are indeed not communism, though in a communist system Medicaid would be the only option. Those are safety nets, not forced equalization of outcomes (state schools aren't really a safety net, and in my view shouldn't exist; governments have a poor track record with education and ensuring everyone has access to it could be done in other ways like voucher schemes).

"A mandate for diversity on corporate boards wouldn't be communism either - it'd be an attempt to undo historical biases that give people unequal opportunities based on their race or gender."

These laws aren't safety nets designed to ensure a minimum quality of life for all. They are communism because they are direct attempts to enforce equality of outcome for only special demographic groups who are favoured by the ideology.