enthusiast dev here, can vouch, having to make a XMPP library for myself for a bot I ran, I HATE the protocol with a burning passion, it's weird and not how you would expect it to be. I'm sure the complexity of the standard didn't help against its downfall. That being said, fully think that it will be harmful in the longrun of Activity Pub for Meta to be jumping in. but there will be some enthusiasts that still use it regardless.