I agree that corporations taking bigger share of GDP is a good point (possibly because of technology / automation / information economy?), but “stock valuations

I agree that corporations taking bigger share of GDP is a good point (possibly because of technology / automation / information economy?), but “stock valuations have increased faster than either profits or the economy” is a red herring. The fair value of a company is the net present value of future profits. To calculate NPV, you take some profit in the future, and discount it to the present by dividing it with the discount rate (usually inflation or risk-free rate), and repeat. Due to FED’s quantitative easing, the discount rate has been historically low for the past decade!