I think we’re in Phase D of Calhoun’s experiment.
https://www.physicsoflife.pl/dict/calhoun‘s_experiment.html#phase-d
https://freerepublic.com/focus/f-news/4114656/posts
I took a quick look at the links you provided. Have never heard of Calhoun's experiment but I think any of us who were around in the 1950's-1960's would agree with you. Things sort of stalled in the 70's then in the 80's-90's it seemed like maybe we were getting back on track. Since the early 2000s it's been pretty clear were headed downhill.
Sometimes I think maybe I'm just projecting the trajectory of my own biological growth and aging onto the culture but more and more I don't think so.