Say what you want about the quality of the game (I personally detest many of its more recent changes and its loss of clear direction), Minecraft has a huge and very, very active community. Notch might not have cracked designing a game, but he's certainly cracked making a game community.

A game that is fun and popular is by definition well designed I would say.

I suppose. I used to find it fun, but some of the changes made more recently have drained much of the fun from it, for me.

Could you tell what changes exactly are you talking about?

Hunger, biomes (although that's an old change now), Endermen, end game.