The data doesn't really suggest this is a real problem. Production has recovered. Employment has not. That should not occur if the problem were AD.

Unfortunately, the real world is significantly more complicated than the Calc 1 models proposed by Keynes.

Production is not a measure of aggregate demand and no-one doing econometrics that I know takes Say's law seriously. Keynes pointed out some of the problems with it oddly enough, but to my knowledge he did NOT propose a "Calc 1 model", although I agree it would be worth looking at if he did.

If aggregate demand were anywhere near the point of full employment, we would see evidence of inflation. We do not. Some prices are rising in nominal terms as the dollar depreciates, but that is quite different.