> Like any federated protocol, extensions don't mean much unless everyone applies them, and that's an almost impossible task in a truly federated landscape. What we have instead is a complicated morass of XEPs that aren't consistently applied anywhere.

The problem is, without actual numbers - how many clients support what - this statement is just a personal opinion, not a rule.

We can say exactly the same about the web. It's also federated, it also has fractured client support (although, sadly, core engines can be counted on fingers) and it's also full of extensions. While I won't praise the web, and I'll surely admit that the trends for siloing are strong (for many, a single big social network site of their choice is the "web"), it still manages to provide somehow decent user experience.