Wow, where to start?
While a game was supposed to be nonviolent, plenty of Minecraft servers seem to have added functionality that allows direct fighting and ability to kill other players. Chat capabilities go unmonitored and "adult language" is widespread.
So do not let your child play, unsupervised, on these public servers. You cannot get to a server without specifically adding the server address (which you typically get by searching on the internet).
On a personal level, it annoys me that a game world with a level of 3d graphics and physics sophistication that was state of the art 20 years ago is extremely popular today, but I can see the draw of "retro" look and feel.
So graphics trumps gameplay for you? I still play my favorite NES/SNES games on an emulator because of how much fun they are, not what they look like.