> What governments should do is spend appropriately to maximize the welfare of their people

Are you suggesting that people aren't capable of spending appropriately to maximize their own welfare, and that the government would do a better job of it (after taking a cut of the money)?

> What governments should do is ... borrowing and spending during economic slumps

Even if this were true, and I think global economic malaise since the financial crisis is evidence it's not, it omits the corollary that governments should then repay debt and save during economic booms. You can't responsibly have one without the other, can you?

> balanced budgets [are a bad idea]

So debt is a good idea? We should finance current spending at the cost of future spending? That's a pretty radical statement. The burden of proof is on you.

And that is what MMT actually suggests, when one do not leave out half their argument.

Their argument is that taxation can be used to take money out of the economy while government spending puts it in. Balance the two and you also control inflation.

His however hinges on the economy being largely self-sufficient, or has tight controls on imports.

Across history, the nations that has gotten into trouble over "money printing" have actually run a massive current account deficit, meaning that they are importing way more than they are exporting.

> His however hinges on the economy being largely self-sufficient, or has tight controls on imports.

So, not actually applicable to the US. (Unless you're going to argue that the US's imports aren't enough to matter. If you want to try to make that argument, go ahead, but it's clearly an additional step that's needed before you can argue that we should actually try to apply MMT.)