Pools are groups of miners. If the pool operator starts behaving badly, the constituent miners will point their hashpower elsewhere.

You forgot a “might” in there.

Bitcoin is more decentralized than Facebook's coin no matter what because mining is controlled by an algorithm, rather than being an invite-only club.

In theory, sure. In practice, the miner implementations are the ones controlling the chain. The only difference is, I can name the CEOs and leaders of many of the Libra companies, I don't know who the leaders of the mining pools are.

Miners don't really have much control in the bitcoin ecosystem.

Also, the composition of large miners changes over time and can adjust organically, unlike membership in the Facebook coin cabal.

If 100 miners meet at the same country club and follow the same government's laws/nudges that's as decentralized as one.