If I were to steal man the argument, I suppose their primary focus is on production. In their view, production happens because consumers are spending. My critique is that production happens because individuals set aside resources to produce, instead of the consume - production comes from previous saving. Your assessment of the Keynesian model is the same as mine. Perhaps you would be convinced if you listened to a Keynesian economist lecture on the topic.
Chapter 10 & 11 Curiosities
Keynesian Shenanigans
The cut-off date for posting to this forum is reached so you can no longer post to it.