So we assume society is an inherent good because we usually live in one?
Society is part of what we are. Being social is part of being human. To live apart from society is a deprivation. Given that humans have always lived in society and probably always will, the point is to make society as beneficial as possible to its members.
If you have doubts about the benefits of society, divest yourself of as much as possible that was made in or by society. No clothes, no books, no computer, no house, etc. If you have learned something from another human being, that piece of knowledge is out of bounds in this exercise. You may not speak any language or read it. Only what you know from direct experience or instinctively can be legitimately used. Try this for a day or even a few hours, and then report back to us.
Another issue is that if you are alone, what moral issues do you face? Don't most moral obligations involve how we act toward others?
Prima facie means on the first look. You did assert that "At a minimum, a good society is one that avoids its own destruction". This implies that a society is not good in relation to how it fails to avoid destruction. Thus on the first look longer lived societies are better in the absence of other morally relevant details. This assertion needs justification.
I said "at a minimum." So a society successfully surviving its challenges is necessary but not sufficient for it to be a good society. I have provided another criterion, the humanist maxim to fulfill one's potential. A good society allows/enables its members to move toward fulfilling their human potential, according to their individual talents, desires, etc.
Also, to clarify, I don't want to put too much emphasis on the outcome of survival. Survival is influenced by many factors, some in our control and others out of our control. What is important is that what a society
can control is responsive to those challenges it faces (internal conflict, external conflict, and environmental threats). All else equal, a good society will outlast a bad society because a good society recognizes the challenges it faces and acts to overcome them.
I haven't described the rules themselves, which is the main way we deal with the content of morality. What I have tried to do is to give a glimpse of a process by which rules are created and then work or fail to work.