The thesis is essentially that meme: hard times, strong people, easy time, weak people, hard times. The authors of the 4th turning explored the cycle from the perspective of demographics, but the concept also overlaps with Ray Dalio’s observations about an underlying 80 year debt cycle. 

It could be just luck, but they did predict in 1998 that a long crisis would begin mid 2000 which seems to be playing out. 

For me, the 4th turning term is just convenient label. We can all see that there is a sovereign debt crisis unfolding and getting worse. The theory gives us a framework to think about possible ways things might unfold.