

A “do everything” app is overkill. I am not a fan of many features Discord implemented over time. But the initial offering of having text chat, voice chat, video chat in one app makes sense. It’s just super convenient to switch the communication type depending on what you are currently doing, without having to onboard and switch between tools.
It’s also hard to draw a line, if you want to go “do one thing well”. Mumble also includes text chat, and user management, ACLs, etc. … for text chat one could use IRC, for user management there are IdPs, and so on. XMPP also doesn’t just do “one thing”. The “X” (= extensible) is heavily used and there are extensions for all kinds of things. Some of the big messengers out there are (or were) using XMPP under the hood (just without federation).

Maybe he’s the right tool for the job