AFAIK the most complained about thing with xmpp is that there are so many standards and every server isn’t guaranteed to implement them. That and just being old which is no curse but people take that as a negative sometimes.

It’s honestly pretty good IMO.

Besides the main implementation synapse being slow, the new implementation dendrite is unfinished but progressing.

But technical standards aside, the hassle of managing encryption keys is too buggy and confusing IMO. That’ll deter most people I feel.

I want it to be great but it just isn’t there yet.