At it's core a civilization is great by its old parable; with old men planting trees who's shade they'll never sit in. That mentality of foresight and willingness to invest in a future they'll have no part in, is at the core of what aligns people with building and developing the transcendental.
And the civilization ceases to be great the moment one generation mostly decides to take the gifts and the giant's shoulder they stand on for granted and instead of investing in the future, they'll rob it, by running up debt or diluting unity by accepting unrestrained immigration, which is just another mechanism for borrowing money for a state (receiving work able immigrants is a short term productivity infusion).
Pragmatism and adaptability is a mark of almost every great civilization, so you have to stuff that in there somewhere.
But for all the wonders of great civilizations, there are always plenty of people inside them living hobbesian brutish, poor lives. Even great civilizations have a gutter. For most of history, that was the majority of people in such great civilizations.
Like when you read about the fantastical military prowess of Spartans, but then remember that only 1 in 20 people in Sparta were citizens, with the 19/20 being slaves.
