(^ timeline assumes playerworld actually succeeds, majority of the time they don't)
But in all seriousness, servers fail because they're too hyped to get working on stuff without actually putting all the time that's needed into planning. Really, really good planning can shave a few years off dev time, and possibly save a good server. And I don't mean just a small .txt with little details, I mean fleshed out stuff. Sketched maps of the overworld(and perhaps even settings, along with REASONS for a town, personalities and histories of the NPCs), lots and lots of ideas, concrete plans that bring everything together, and a firm, firm idea of what you want.
If you're talking about classic servers... oh, I dunno honestly. Just something doesn't tick for me to bring me in. If I wanted to play an RPG, I'd go play one of the many better ones out there. Era is too laggy for me(I've played 3D games where lag wasn't that big of an issue for me, being on 56k). Hmm, and others just don't seem to offer much. Maybe some would be nice but they insist on ass-ugly tilesets that burn my retina's and push me away from the server. As for the 'classic-type' servers, they offer no direction. I like exploring, but I hate randomly running around doing mindless things hoping I find a quest, and then finding one only to see it's kill a bunch of baddies or push a million blocks. Then find there's nothing to do with the fullheart I gained because the server is dead.