The end of exponential population growth as the Earth has already filled beyond its carrying capacity predictably eliminates all sources of growth except productivity growth. Previous generations could depend on a population and resource extraction growth boost of 2-5% per year, but that will pull back to negative drag as population of first world peoples shrinks and affordable oil production drags. That 7% growth is now equivalent to 2% in the conditions today's people will retire into.

I'm just eyeballing this, but after adjusting for inflation neither recent stock nor bond yields look out of the ordinary, historically speaking.

There are always reasons to expect growth to go down, and other reasons to expect it to go up. It isn't clear to me why cherrypicking solely from the former group is supposed to be convincing.