“What’s the point?”
We have everything we need, and we realize that everything we still want is mostly just for the sake of having something to want.
We’re not on top, but we’re comfortable and stable and cozy. We realize that there’s something unfulfilling about this lifestyle, but there seems to be no reasonable way out of an existential neurosis that was brought about by reason.
Enemies and rivals help, but you can only leverage those so much before it becomes quite obvious that your enemies just want to eat, sleep, and be merry just like you. Never mind the curse of actually losing all your rivals, should you become dependent on their existence for your cultural solidarity…
There are stresses in the world, old enemies, the nettlesome annoyance of various occupations, border squabbles, etc., but as long as no one backs anyone else into a corner(and no one has any logical reason to do so), it seems civilization is destined to keep cooling off until a powerful nation becomes stupid enough to get really fired up over something ridiculous, or perhaps some actual critical material shortage surfaces?
So, maybe instead of trying to preserve your culture en-masse, you concentrate on maintaining a little island of it, amidst the sprawl and decay, as a pilot light, for when the time comes that people get desperate, and hungry, and perhaps even angry enough, to get the point.