There's a massive difference in the decentralization of Ethereum's PoS implementation vs. Cardano, which uses delegated PoS.
If only there were other PoS chains.
How so?
Ethereum uses signature aggregation to allow for a very large number of full-fledged staking nodes. Most PoS chains have a small number of full-fledged nodes, and everybody else delegates their stake to one of those.