I think the root of this disagreement is the misunderstanding of what MMT actually is. It's certainly not how the bourgeoisie currently use the economy - exactly the opposite in fact, because the US economy is almost completely controlled by finance capital i.e. those using debt to extract money in an M-M cycle (and cutting out the commodity form M-C-M of industrial capital). Implementing MMT - I should say, the productive insights of MMT - requires the government, or a government-controlled central bank, to be the only one capable of creating and lending money. It would do so solely for the purpose of mobilizing workers and resources, not to extract interest on debt payments.

Because it no longer needs to make a profit, it can also write off debts if paying them down becomes impossible or would damage the real economy. China, where the banks are directly controlled by the government, did exactly this - a steel plant built using a government loan became unprofitable during the pandemic, so they simply wrote off or wrote down or froze the loan (I forget which) and kept the plant and its workers ticking over until demand rose again. Whereas, in the US, the plant would have been scrapped and its components sold off to pay its creditors. And the US government would have been powerless to stop it, indeed would not have even tried, because finance capital is the ruling class. It's true that the US already kind-of knows it has unlimited money when paying for military spending, but even then large chunks of that are spent by defense contractors on stock buybacks to inflate their worth so financialization is taking its cut there too.

Foreign trade, unequal exchange etc. are on a completely different axis. MMT is only concerned with mobilizing resources within the region that the government has monetary sovereignty over. The US ability to demand resources from other economies is due to the dollar being the world reserve currency, the most stable commodity for storing wealth in while trading, which is ultimately due to the US' prime position after WW2, its (then-)enormous industrial capacity and its overwhelming military power. This is what enabled US monetary imperialism - because trade was only done in dollars, in order for small countries to buy necessary goods, they must have dollars. And the only place to get those dollars were US financial institutions like the IMF and World Bank.

If those countries had had the tools and resources to run a self-sustaining economy, including producing enough goods for international exchange to cover things they couldn't produce themselves, they could have implemented MMT and been independent the whole time. Instead, they're slaves to the dollar debt from the IMF and World Bank that they needed in order to buy in necessary goods from other countries. And the conditions of those dollar loans are always the same - austerity and tax cuts, the exact opposite of what MMT suggests. So they're backed into a corner, desperately trading anything they can for dollars to get the food and medicine they've been forbidden from producing themselves, and their goods can be bought cheap by multinationals to sell on at an inflated price in the imperial core.

But this doesn't address class war, except in that the ruling capitalist class will obviously never allow it to be used to its full potential - which is why I suggest it as just one weapon in a Marxist party's arsenal. But others in this thread seem to be treating it like an ideological position rather than what it is, a scientific description of money, and more importantly one that is (to the moderate extent that I have investigated it) true. Like, it's just true that money is created from thin air by governments at the moment they spend it and then destroyed when it is taxed back. It's true that a government can create as much money as it wants, as long as that money serves to increase the forces of production. These are facts that any communist government will have to reckon with, and past and present communist governments seem to have done so already, to their advantage.

However, while writing this and reading other comments, I've realised that maybe I actually am the one missing something. My understanding comes almost entirely from Michael Hudson, who has definitely read and refers constantly to Marx, especially Capital vol. 2 and 3, but then another poster said he isn't an 'MMT guy' and that MMT isn't Marxist. And I haven't read anything from any of the other 'MMT guys', from which I'm gathering there is some kind of classic liberal ideological component that this could be done under capitalism if government officials just had the right ideas. But somehow or other I've been shown the scientific model above, and had it empirically verified to my satisfaction - including its usefulness to a revolutionary government - so while I'm no longer sure whether or not it's called MMT I still believe it's a useful, even vital, thing for communists to know about.