"Throughout the 1970s and 1980s, baby boomers, in their youth, swamped the system, increasing aggregate demand, and forcing double digit interest rates and sky-high inflation on the economy. Some thought this was the new norm, but it was aided by a significant demographic blip."

A good point IMO, which often gets ignored by contemporary economists.    

However, if current aggregate demand is weaker than expected, it is not, IMO, only because of the demographic shift.   There are a lot of factors at play....I do hope that you are wrong about rates staying low for the next twenty years -:)   But so far you have been right (and I have been wrong).  As a "saver", not a big fan of zero interest rates.