Ah. This is what I was missing. Thank you.

Still seems like the existence of global trade would wreck the concept, but I’m sure the krugmans of the world have explained that as well.

“When people expect inflation, they become reluctant to hold cash, which drive prices up and means that the government has to print more money to extract a given amount of real resources, which means higher inflation, etc... Do the math, and it becomes clear that any attempt to extract too much from seigniorage — more than a few percent of GDP, probably — leads to an infinite upward spiral in inflation. In effect, the currency is destroyed.”

I think that minimizes the differences and potential for catastrophic outcomes inherent in MMT. What you described is Keynesianism which has been politically dominant for a long time. I think MMT obviously has similarities in advocating for an active government role but I think it goes well beyond the above.

Keyensians suggest what you mentioned: stimulating or contracting the economy when it experiences a recessionary or inflationary gap. MMT argues that the reason that an economy experiences a recession in the first place is specifically because the government isn't spending enough as opposed to Keynesians who argue that when there is a recession the government should increase spending/cut taxes to increase output. I admit that those two perspectives are similar, but I think MMT makes a very important shift from government having a role to support or fix to having the main role in driving an economy. MMT is attempting to provide intellectual cover for a dramatically more expansive government role in the economy than Keynesianism.