According to the Keynesian worldview, this is really important. They're not correct about what they say about empirical data. The level of aggregate spending in the economy is not a lever with which you can control inflation and unemployment. Inflation goes up, but also unemployment goes up because this model is broken. That's not how the world works. So what would a scientist do? What would a non-huckster do in this case? Admit the theories wrong and find another way to reformulate it. Have the Keynesians done that? No, still the same garbage in the textbook that is being taught until today.