The choice is not between MMT and not-MMT
We already have at least a form of MMT*: Covertly, and for private purposes, instead of openly and transparently, and for public purposes:**
MMT is not just theoretical. In effect its greatest practitioner, without admitting to it, has been the Republican Party in the U.S., but only when in power: it cuts taxes to the wealthy and increases spending on prisons, the military, and war, and lets the deficit increase. And it works. When the economy is depressed, economic growth, job creation and deficits increase, and inflation and interest rates remain low. Progressives would not want to use MMT that way. We would want more jobs, producing civilian goods and services, fairly distributed, while subject to the constraint of potential output. And we would have the federal government spend tens of billions more annually on the programs and infrastructure we so desperately lack.
Of course, it's to the Rs advantage to lie, and so they do. And by the Rs I mean the Ds, too.
NOTE * This reminds me of the famous question of a French philospher: "But will it work in theory?"
NOTE ** This implies that the debt/deficit discourse in our famously free press and among thought leaders is completely bogus, impacted bullshit. Well, yes.