There are very few missing pieces for a game like MTG. The main reasons we don't have a Stockfish for MTG is that it's a PITA to implement the rules and that nobody cares (or at least not enough to make it happen.)
There is nothing that, in principle, makes MTG different from poker or bridge, and we have superhuman engines for both.
There is nothing that, in principle, makes MTG different from poker or bridge, and we have superhuman engines for both.