MMT advocates want Congress to run the economy? Are you out of your freaking minds? They haven't even managed to pass an actual budget in the better part of a decade!
Let me tell you a secret, Congress ALREADY runs the economy. They just ACT like they don't. Notice they had no issue implementing tax cuts (increasing money supply) AND increasing military spending (increasing money supply). They act like they don't because otherwise, people might wonder "Hmm, if they can do that for the rich, and they can do that for the military, maybe, just maybe they can do that for me!". And then people might get strange ideas like, maybe we can afford universal health care, maybe we can have a system oriented towards their needs.
So Congress doesn't want the people to know they already control the economy, because otherwise, people might want them to do the job they elected them to do.
There is a good case for the exact opposite of what you suggest. Congress pretends like they have power over the economy, but at best they have minimal or random effects. They promised economic growth with tax cuts, but what are the real effects? hard to even tell.
MMT advocates want Congress to run the economy? Are you out of your freaking minds? They haven't even managed to pass an actual budget in the better part of a decade!