"The protocol has been extended" has been XMPP's theme for decades, and also its problem. Name your favorite client, it probably won't have several extensions, and a lot of useful things require support on both ends plus the server. Lots of things that should be ubiquitous are not, including s2s auth. There needed to be more structure, like AIM back then or Signal now. Also the XML stuff is a nightmare.
Even if Google Talk kept XMPP, they weren't going to save it, cause nobody used Google Talk. Facebook was by far the biggest XMPP-supported platform (though it wasn't federated), and they stopped probably cause they didn't see enough clients. Even Slack supported XMPP for a while, did you use that?
Even if Google Talk kept XMPP, they weren't going to save it, cause nobody used Google Talk. Facebook was by far the biggest XMPP-supported platform (though it wasn't federated), and they stopped probably cause they didn't see enough clients. Even Slack supported XMPP for a while, did you use that?