Here is an idea, based on Mass Effect. Instead of a permanent state of maintaining what civiliziation there is, there could be a repeating cycle of failure and new attempts. But every time, the result is a little bit better than the last time.
A constant process of self-improvement, both as indivdual people and as entire cultures. Which I think fits well with the aspect of moral ambiguity. While PCs are supposed to be flawed and subject to the prejudices of their cultures, players are also supposed to strive for improvement. Not that they arrive somewhere and everyone is happy and there is no more conflict, but the underlying assumption that the current state of things can be torn down and replaced with something better. Like removing a bad ruler and replacing him with someone a little less bad. Or sparing a villain and making him do something useful.
And on a larger scale, settlements and whole cultures emerge and disappear over and over. New settlements are founded all the time, others get abandoned, and some are built upon by latter inhabitants. There are signs of earlier settlements everywhere, that can be explored or also serve as reminders that everything gets eventually replaced by something else.
But in the long run, it's about civilization as a whole surviving against the dangers of the Wilderness, under the assumption that the present is at least somewhat better than the past, and that things will be somewhat better as time goes by. Nothing radical, like suddenly democracy breaks out, but a feeling that everything new that is build is temporary, but does help a little bit in the long run. As opposed to "we keep on surviving as long as we can".