[notahacker]

I can't think of a single macroeconomist that would say "but the money multiplier" though. This is a straw man invented by MMTers to avoid debate.

Literally every single central bank's policies are designed and implemented by mainstream macroeconomists, as were the capital requirements. "Banks can lend always anyway if it makes business sense" is the system mainstream macro built. Of course, mainstream economists also consider the "if it makes business sense" bit (and to a degree the "capital requirements" bit) matters, and have models observing that the flow of money actually injected into the economy at a given interest rate being finite and relatively predictable, and they can make it go up or down in different circumstances by changing that interest rate. They also (since the 80s, at least) have a sophisticated enough grasp of inflation to figure that how the dollars are injected into the economy matters rather a lot.