What is Modern Monetary Theory?

[Lexicus]

That seems like a misrepresentation of it's intent, implementation, and outcome, but I'm not really qualified to speak on it.

Kind of. Y'all keep treating MMT as something that could be 'adopted,' that is not true, it's a theory that describes what is going on. You could adopt some of the related policy ideas but those are not "MMT" as such.

What Republicans have been doing is better referred to as "functional finance for the rich."
https://en.wikipedia.org/wiki/Functional_finance
Functional finance is an economic theory proposed by Abba P. Lerner, based on effective demand principles and chartalism. It states that government should finance itself to meet explicit goals, such as taming the business cycle, achieving full employment, ensuring growth, and low inflation.

Now, that is misleading because it isn't really an "economic theory" so much as an economic policy guide or recommendation. It says, in essence, that you target these goals of full employment and crisis-mitigation, and allow the government's balance, the exchange rate and so on to "float." The Republicans are allowing the government's balance to "float," driving up the deficit without a care in the world, so that they can give massive amounts of money to rich people.

There is a deeper bias being expressed, which is that the private Market is what creates things that people want to buy. That it is the market that generates dollars that the government then taxes.

One of the points MMT makes clear is that this bias is, literally, just wrong.