why are we still stuck in Keynesian macroeconomics? Govt spending did not solve the fundamental problem that was the great depression. Glass-Steagall did. Our growth of the 40s and 50s was due to the influx of educated workers with a good work ethic. Not by any miraculous govt action. All the govt did was build a factory (the military - industrial complex) for these people to apply their skills.
We are now in a fundamentally different crisis. We lack the motivated, educated workforce and therefore have come to rely on a different form of income-wagering. We have become skilled at gambling (the lottery was nonexistent in the US 40 years ago), speculating (derivatives did not exist 40 years ago) and short term rewards (most corporate discussions since Enron are about compensation of the upper echelons of the executive suite in terms of stock options, vesting schedules and not prospects for long term investment) Fear of disruptive technology invented in a garage has everyone looking at the immediately obtainable rather than the future.
Keynesian policies will not fix this. Instead of creating demand for public works projects, the govt has to start regulating education so that tuitions are not stratospheric, so that students get tax credits, so that people with a healthy lifestyle get tax credits. This is far better than printing money - a fungible value metric that has no moral compass nor any incentive for real personal growth.
I think you are partly right with the influx of motivated and educated workforce. But I disagree with Keynesian didn't have an impact. The government spending did help American recover back in the 40's, 50's and that's because of the following reason:
1) There are demand for the factories, government projects that American was investing with debt at the time. After WW2, there was a huge demand for everything around the world because much was destroyed
2) and in addition, not many countries still have the manufacturing capacity American had, so there were little competition for the supply to meet the demand so the investment with debt/deficit had great return
3) American was good at what it did back then. American had the manufacturing capacity, efficiency, nobody else was close to American capability. Again, this made the investment with debt justified.
4) American government was less worried about "Political Correctness" and wasn't that crazy about projects to make some liberals feel good about themselves. It was all about economy and improving the economy.
All the above factors allowed the government spending to have immediate and effective impact on both the employment and the economy.
Now with bunch of crooks in the government, stimulus are invested in programs (many due to PC) that doesn't produce economic return, like green energy. American companies are no longer competitive, and the economy in the US and around the world lacks the demand to digest whatever investment government spending will be on.
It's not as simple as spend money you shall solve your problem. Keynesian policy certainly isn't a magic bullet for all problems, sometimes it will work, sometime it won't. This is something zombie economist around here with only the ability to google won't understand.