Matrix is awful. I don't know if that's still the case but when I tried it a year ago it took me more than 30 minutes to get it working. In discord, you sign up with email (very low friction), click the + button and boom. You've got a private server you friends can join by clicking a link. It Just Works and until an alternative has this level of convenience Discord is not going away.

This is to say nothing of the insanity of public, effectively unmoderated rooms on Matrix.