MUDs never disappeared. People stopped finding them engaging enough to use. Blaming Discord reverses the causality. MUDs lost engagement long before disco was created. People congregate on disco because it offers a more compelling social interface, even if it lacks the depth of a persistent game world. The opportunity I'd draw from this isn’t to convince people to return to older and less engaging interfaces. It’s to build persistent roleplaying systems around the interaction modes that have proven to be more engaging already. Potentially combine voice, speech recognition, text, tts, and synthesized characters with a proper world simulation underneath. If roleplaying communities already gather in disco, then deliver the experience where they already are. The interface was always irrelevant to what made MUDs fun anyway. Imagination and connecting with other people was always the thing.
I specifically outlined non-MUD role playing environments because I know MUDs lost popularity long before Discord. I am outlining that any form of tech, besides Discord, is sidelines -- MUDs and a hopeful resurgence as well.
Is your autocomplete passing you disco instead of Discord and you're just going with it? Or are you implying that before the creation of disco music people had grown tired of MUDs?