It's too bad you can't live in modern day Saudi Arabia, or Venezuela, or 1830's France. Then you could see that quality of life is in fact tied to an economy and an era, among other things.
If you don't trust me, Steven Pinker has a great book on this -- Enlightenment Now.
Those factors don't account for individuals, only on generalities. Something like the original post assuming, tongue in cheek, that the Boomer generation was better than the Millennial generation. There were unhappy and poor people in each era, just as there are happy and prosperous people in times when the general quality of life was bad. When I say poor and prosperous I don't mean just wealth, its also having a job that one loves, a place one is at home in, respect in one's community, good personal relationships and the like. Wealth is a factor, but a small factor. Some of the most unhappy people are the ones with the most money, who use their power to make other people unhappy so they will have company.
I agree that in times of turmoil, quality of life goes down for all in that society. With that said there are those who make the changes needed (go elsewhere or establish a position that takes advantage of the turmoil), who will have a better quality of life than those who are unable to handle the turmoil. In Saudi Arabia, those who like authoritarian theocracies are happy, those who don't like being that controlled are unhappy. That was true in the Soviet Union, China and other places. Some people in the US are advocating that we become like those countries right now, demanding that we become a socialist or communist country rather than a republic based on capitalism.