Here's a fun one, which is probably quite fedi-relevant.
I am part of a disparate group of people, who all work together for a common cause.
We generate a *lot* of email traffic.
I am old. I like email.
Other people... not so much. (As in, they don't like email as much as I do. Not that I don't like other people that much. True though that is.)
But what is the alternative?
I use IRC, XMPP, and Signal, but not Matrix. And the last thing I want is a deluge of IMs, where searching history is tricky.
Others like Matrix. These things could be bridged.
A forum is fine for some things, but not real time chat.
Mattermost etc. feels like yet another thing to monitor (or bridge).
I guess that I'm unpersuaded that more channels is the answer. Perhaps fewer communications with so many people - but then people like to be "in the loop".