“When I say that, I mean that proof of stake is (1) claimed to be a consensus system, and (2) constitutionally incapable of actually producing a consensus.”
Proof of work burns electricity so that rewriting history costs something real. Proof of stake replaces that cost with coins the validators already hold. A chain secured by whoever owns the most tokens is a shareholder vote with extra steps. The people selling it as decentralized tend to be the ones holding the most stake.