The MUD I play (Aardwolf) averages about 200 players online at any time, but it's effectively dead as a MUD. There's very little player interaction, which is what made MUDs special originally. Part of this is that nearly all multiplayer features have been abandoned, and the rest of the features are centered around loot box equivalent features. Despite this, there are a couple hundred people who seem to enjoy the gamification. The MUD is highly optimized for scripting, so it scratches the side project programming itch for me.