What caused macroeconomists to criticize the Old Keynesian theory?

The stagflation of the 70's.

Worthlesser is right - the high inflation mixed with high unemployment did not follow Keynes' aggregate demand curve and made economics remodel the relationship between these metrics.

Quantitative Easing is a Failure. QE is seen by its adherents, such as former U.S. Federal Reserve Chairman Ben Bernanke, as both the panacea to heal the post-global financial crisis world and also the factor whose absence was the main cause of the Great Depression. This is in line with their view that central banks create currency for commercial banks to then lend on to borrowers and that this stimulates both asset values and also consumption, which then underpin and fuel the various stages of the expected recovery, encouraging banks to create even more money by lending to both businesses and individuals as a virtuous cycle of expansion unfolds.

The theory sounds great.

However it has one tiny flaw. It’s nonsense.

Macroeconomists are a little like proselytisers for religions, Catholics, Protestants, Moslems, Hindus, Buddhists etc., They all say that they are right and everyone else is wrong.

When has it worked? That might be the driving reason why they criticize it.