This^^DaveYanakov wrote: Minecraft would be a lot better as an engine, I think, if Notch focused on making a world building sandbox first and then put his full focus on making a game that works in it.
He started out that way and it was the reason I bought the game, for the sandbox building/tinkering aspect. While adventuring/spelunking/exploring are fun, it doesn't take very long before you get bored.
Notch has a bad habit of second guessing his design decisions. Like when he first said he wouldn't add an experience point system.