For what it's worth, I wholeheartedly agree with that microeconomic assessment.

Macroeconomically, banks do act endogenously in adding to the supply of money (as credit) based on current relevant variables. Even the central bank bases its decisions regarding the creation of 'new money' (currency) on general economic conditions.

A fully exogenous supply of money would be based on a variable outside the economy altogether, such as, say, demographics. As it happens, I have developed a paradigm in which currency is supplied to the economy in precisely that way. The results for society, it turned out, are astonishing. I am an amateur political economist, but I do have an M.A. in the subject.

If curious: "Paradigm Shift" (here in Medium, but not behind the paywall).