It is based on default and MTG. It has many new mods, unique mods, and customizations that make it much more than default. Your comment seems shallow and unhelpful. It makes me skeptical that you've played it much at all.
Whatever base which was used isn't important. What matters is the design of the game. Minetest game's old, but provides a starting point. And why didn't he make use of mineclone? Perhaps because it contains many unique features. The more complicated the game is, the harder it is to customize it.