It’s basically impossible to be fully decentralized. Even if we’re sending around IP addresses to each other, they’re still attached to your ISP. Federation and decentralization aren’t the same thing (which I’m sure you know), so I think we can agree that Twitter’s rationale is mad gay.
NEETzsche, they keep pushing the idea that a public key is a valid form of identity. I keep responding to that that in the real world, account recovery and access revocation are hard requirements. People are terrible enough with passwords, and you expect them to both keep their private key secret and not lose it. This kind of thinking is just plain delusional.