Why would anyone listen to him? He is the one who predicted that the US economy would fall into a major recession within 18 months of Trump’s election. He’d be exhibit A in the proof of Buckley’s comment that he’d rather be governed by the first 2000 people in the Boston phone book than by the faculty of Harvard that Summers once presided over.
He mixes in half truths. True, any socialist economy (Europe, Canada) is going to have a hell of a time producing above 2% GDP growth in years to come. The size of government, the existence of corporate welfare, and demographic collapse in population are going to pull hard on any growth.
America is not that though (not yet). It is a vibrant, competitive economy with high productivity. So it can do so - and with the corporate tax cuts - should be a no brainer.