It’s often said that people disagree just because they don’t understand each other. I do indeed understand MMT, and I don’t think proponents understand humans. The varied “if this, then do that” in the theory all work. It’s just humans don’t tend to do the things the theory requires. Sure, we can stimulate the economy with more money printing. It’s just that people with the taste for that never do stop nor tax back the resultant inflation.
We can even explain this to people who have no idea of economics at all. Here’s one way of putting it: Politicians can spend as much as they like on whatever, and if it goes too far they can just raise taxes. Sound like a deal? It could also be described as follows: Giving politicians a blank checkbook and telling them to go have fun is likely to work out well, right?