We use the term “Keynesian” loosely to stand for economic interventionists of all schools. The followers of JM Keynes and Milton Friedman alike fit that category. So do some of the more rabid supply siders who claim the power to stimulate ultra-high economic growth with the tools of tax policy alone.
The common denominator is economic statism. That is, the assumption that the state, including its central banking branch, is indispensable to economic progress and prosperity.
As the various denominations of the Keynesian economic church have it, capitalism is always veering toward the ditch of under-performance and recession when left to its own devices and natural tendencies; and, if neglected by the wise policy-makers of the central state too long, it lapses toward outright depression and collapse.