It does miss an important feature.

I'm frequently on a mumble server that can have 1000 people on it at the same time. A channel hierarchy is vital to global broadcasts from command, allowing foot soldiers to shout important information to command, allowing platoon leaders to communicate to their subordinates, allowing squad leaders to communicate to just their subordinates, and allowing the foot soldiers to chit chat to just their squads.

Discord is fine for playing video games with friends, but its voip is a nightmare for actually organized groups who are voip power users.