World of Warcraft actually made it very easy to use a custom server, since you'd just need to change a hostname in a single text file and the client would connect to it instead. Not that it was allowed but from a technical perspective it was quite supportive. I think it's no longer as simple but there's still private server projects around.
As a broke college student, I had a great time playing on third-party servers. The experience was janky, of course, but it was hilarious. I made some good friends there.
Then I had to stop playing because it was eating into my study time too much.
I've tried going back to MMOs a couple of times since then, but nothing seems to have the charm of a smaller community like that.
