That's of course true, but that's not any different from today on any blockchain that I know of

It's not different. It's nevertheless a source of control and staking intrinsically centralizes that control as well as just handing the keys straight to staking pools because of the utterly idiotic $50k minimum stake for non-pooled users.

On Ethereum specifically, should a group of stakers collude to gain 66% share of the validators and censor transactions, the community would fork those validators off the network, making their money worthless, so I think it's highly unlikely to happen.

This is utterly hypothetical, and an idiotic hypothetical at that because of the bad assumption that people would stake all their money.

If such an attempt was made, the whales would dump their coins on the fork, crashing the market price, and losing everyone who participated in the fork most of their money.

I know Coinbase, who is the 3rd largest staker, has publicly stated that they not will participate in any censoring, and would rather cease operating validators.

"Ceasing operation of validators" is participating in the sanctions.