It always feels great seeing Mumble mentioned, especially with such a positive sentiment. I was a core dev, or am but have been mostly inactive for a long time now.

Discord with millions in funding and a dev team - Mumble with contributors you can count on one hand obviously can’t keep up. If a community wants text messaging, that’s just not Mumble’s target of primarily voice communication. Whether that’s because of limited resources/people or a deliberate target scoping.

My clan briefly switched from Mumble to Teamspeak for a while. I was happy to see that the majority preferred Mumble and we moved back to Mumble back then. That was still before Discord was a thing.