Keynes wrote from the perspective of a gold standard and the constraints that it imposed on the economy. His ideas, while well intentioned and correct for his era, are no longer relevant and haven't been since 1943 when FDR ended the convertibility of dollars to gold domestically. The final global end of the gold standard was enacted by Nixon in '71 when he removed us from the Bretton-Woods agreement.
The next evolution of economic thought has been long delayed by neoliberal think tanks and the influence of the ruling class in our media and government, but it is rising in political circles as surely as the sun illuminates the landscape each morning. MMT is an accurate description of our monetary system that dispels the many myths and outdated restraints on the people's government that makes them subject to private banking and the whims of oligarchs.
The full force of orthodox economists and conservative politics is now being brought to bear on the proponents of MMT, but their influence will not be denied for much longer. The popularity of such politicians as Bernie Sanders and AOC is largely due to their understanding of MMT macroeconomics and what it means for a sovereign currency-issuing government that is not revenue constrained. If the general population were to experience a universal epiphany of economics with a sovereign fiat currency it is likely that many politicians would find their heads adorning the light poles in our capital.