The problem with MMT is this: It might work if you spend the money on infrastructure. But who's going to be making the spending decisions? Congress is. Do you trust Congress to spend the way MMT says they should? I don't, not by a long shot. Congress will say "Free money? Great! Ponies for everybody!" or something equally wasteful.

MMT might work (though I doubt it). MMT being run by Congress terrifies me.