> eventually the system will hit a tipping point that results in either hyperinflation or (more likely) a debt default.

Neither of which are even close to occurring in the United States.

Politicians are going to politician. Just look at the “dynamic scoring” models republicans apply to tax cuts. It isn’t the job of economic theory to ideologically reign in politicians, it’s job is to model to world accurately. I haven’t read enough into MMT to actually assess that for myself, but it’s ridiculous to assert that it’s flat out wrong because politicians run deficits (which they have done for decades before MMT even came into existence)