I often think about the city-states along the Silk Road: healthy, peaceful, cultured, unprecedented prosperity for their time. All defeated when the hordes of Genghis Kahn rode by, many utterly destroyed
The Empire of Mali. The Kingdom of Lithuania. Macedon. Tyre. Babylon. Carthage. Samarkand. Assyria. All once mighty, all gone, perhaps a place-name remains, if that
For anyone still paying attention, I should have written "The Grand Duchy of Lithuania", which was a powerful state for hundreds of years in the Middle Ages
The Kingdom of Lithuania, while also powerful, lasted about 2 years
Aside from perhaps Macedon and Carthage (indirectly via Rome) most of those don't even warrant a mention in the high school history curriculum (in the US, at least).
The simple fact is that pre-industrial history has had literally thousands of different thriving civilizations around the world. It's simply not possible to even briefly cover anything but a fraction of the more "important" in a non-university setting.
Maybe, but it is not because we tend to be overly pessimistic in general, that serious problems cannot happen to us. Entire civilizations have diapered in the past, so we should remain vigilant.
After all, another bias that humans have, is a strong tendency to believe that what is true now, will remain true forever.