Distribution of hashing power requires capital investment and so tends to centralize. Capital investments to issue proof of stake coins that keep wealth re-distributed are negligible.
What do you mean by centralization? Concentration of ownership of
means of production?
It is a moot point at best, since we have a multiplicity of
cryptocoins that can be mined with consumer-grade equipment. Your
critique makes sense only in the context of Bitcoin maximalism. But
you yourself already invoked the altcoin environment with its many
opportunities.
As for PoS, the difference is only of a degree, since significant returns
can be obtained only by heavy investment. And any perceived
differences in the fairness of the two schemes are, I am afraid, offset by
the flaws in the fundamentals of current PoS implementations.