I'm not sure if I buy the whole #meta #facebook killed #xmpp. I've seen several services, with large user bases, using xmpp, or some abstraction of the same protocol. I don't think the concerns are invalid, I just think there's a bit more to it.
@aboxofsox
My take on the "bit more"s: For sure FB Messenger or GChat didn't kill XMPP. But they exacerbated the Federation fault lines built into the protocol. There Federation is a bilateral agreement. So if a big node refuses to federate small nodes are blocked out. That is what happened. I don't think the services you identify federate among themselves. It is my opinion that these two deciding to opt out of federation gave license to second stringers to opt out as well.
@aboxofsox
In contrast, to date the default posture in Fediverse is to federate w others. Defederation of the whole node is considered to be a nuclear option. Even with Meta. The fear is losing this outlook on federation.
@aswath I see. It's more of an argument for the anti-federation rather than "Meta/Facebook killed XMPP". I think that's much more reasonable and can agree to that. Then at what point do you move away from XMPP to meet business needs? Or maybe that's a question federation isn't equipped to address if you were to maintain that culture.

@aboxofsox With the advent of WebRTC, loss of Federation is not of concern. If your node refuses to fed with mine, I could share a WebRTC link with you, so you can init a chat session w me.

I am not sure that kind of escape mechanism is readily available in AP based Fediverse.