Yeah, some are bogged down in politics and dominated by a few Methuselah with ego problems, but I've played plenty and those are in the minority and stick out like sore thumbs. Keep away from MUDs that take themselves too serious and you're good. Or look out for freshly established ones.
Aardwolf would be one example with a very friendly population. Gamewise it's a hodgepodge of creative writing and doesn't follow any strong guidelines.