Additionally, there are concerns about having the government itself involved with regulating inflation and business cycles. An independent Fed, at least in theory, allows for the fed to take a longer view of the economy even if politicians have incentives to care only about the next election cycle. All it would take is one conservative majority congress to semi-dismantle any MMT mechanism and completely mess up any "controls" put in place by MMT proponents.
That being said, it is refreshing to have different ideas being taken seriously enough to enough mainstream conversation. I don't think the field of economics is "solved" (probably far from it) so I think good ideas that challenge the status quo are generally good.
One liberal majority Congress could do the same. They might dismantle in a different direction, but it could be just as disastrous.
However, the gutting of the policies by another administration is what scares me in regards to MMT. I'm not sure that incremental changes work with monetary policy. MMT in particular seems like it needs some big, systematic levers in order to actually function properly.
That being said, I'm happy to be wrong about this. MMT being viable would open a more clear path to something like universal health care.