Alright, full disclosure, I still really like Minecraft, but I've never gotten heavily into the social/multiplayer side of it. I've tried hopping on a few popular servers, but in more than one instance I saw the words "High School Roleplay", which prompted me to cringe and leave. Minecraft is definitely on the decline, but I think that has more to do with the constant influx of young and immature players than it does anything else.
While I am certainly no SethBling, I like to build large, complex, nice looking architecture, and I've found that there are surprisingly few people with that capability, even within my age group. My best friend, for example, lives almost exclusively under ground in a rat's nest of hastily carved tunnels when he plays.
I've been part of 6 small servers, and the typical progression goes something like this... I am given a place to build. I build. My neighbors all see and praise my building. My neighbors then either ask me to help them with their builds -or- get discouraged and move or leave the server. Eventually I am basically playing single player, only with lag. I've hosted servers as well, and tend to get this same thing happening, only I end up building a large and involved world that folks tour through, compliment, and then leave.
*sigh* So now I just play singleplayer, and if I do anything I'm particularly fond of, I might publish the world file somewhere.