Update: You could call this half right in retrospect. Fiscal policy is ineffective except when monetary policy is ineffective, and the Federal Reserve didn't print nearly enough money but the money they did print did prevent another Great Depression. We would not have been better off if the Federal Reserve had done nothing, thinking all their plans ineffective. There might be some kind of lesson here about EAs who fret about "What if we can't model anything?" whose despair seems kind of similar to Eliezer_2009's.