I mean, all of those civilizations rose and fell, so there was certainly a point at which the productivity level was no longer sufficiently globally dominant.
Some historians say that the main cause for the Fall of Rome is rising inequality. Initially, society was mainly based on small farmers/warriors, doing war close to their home.
But as Rome grew, wars tended to get farther and farther from home, so farmers could no longer tend to their farms, and also large influx of slaves made them noncompetitive against large slave-owners. So they had to sell their farms to those large owners, exacerbating the problem even more.
I honestly don't know any single revolution that happened for any reason other than inequality.
That's the thing, everyone can be right here. You don't want to regularly yell "fascist, racist, pimp, rapist" or the power of those words disappears. At the same time, if you refuse to use the words when they apply, then their power is irrelevant. Stability breeds complacency, complacency breeds contempt, contempt breeds instability.
The Kids perceptions and mores change every generation (both in some multidimensional average and in their dispersion) based in response to their elder's beliefs and their material conditions. Those changes could be destructive or not, but the idea that "there is no truth" or we've reached "the end of history" mark a more dangerous part of the cycle.
