The timing of fiscal policy
So Monetary Policy arguably works in part because of the credibility that central banks establish that they will work towards inflation targets as best they can regardless of political headwinds. While Milton Friedman pointed out in “The Effects of Full-Employment Policy on Economic Stability: A Formal Analysis” that counter cyclical policies are formally impossible to time correctly due to delays in information coming in and the effects of policies taking time to work on problems that may have changed in scale after the data is received.
As well, fiscal policy is not driven by overall health of the economy in the same way that central bankers tend to operate but by the. Short term and localized interests of elected officials.
With all that in mind, how does a predominately fiscal policy framework propose to address issues that a monetary framework can barely do? Assume I am accepting all other premises of MMT as valid for this discussion. For further context I am an American so any presumption of fiscal competency in elected officials is aspirational at best.