Here is a somewhat heretical thought..
All ‘civilizations’ and cultures are about maintaining the status quo.
As I have noted in a previous article, breaks in order are necessary for new ways to develop. However in time even these new ways stagnate by becoming civilizations or cultures.
and that is the problem!
Even a novel worldview will ultimately become just another set of dogmas supported by a new priesthood who will not adapt to changing conditions. Since the world around you changes, both in terms of conditions and what other people are upto, all dogmas will ultimately hit a series of obstacles which will ultimately destroy them. The supposed resilience of cultures is due to forced isolation (pre-meiji Japan, pre 1950-China), “insider” societies (India), extreme poverty (Africa) and simultaneous screwups by multiple groups of people (800-1500AD).
Even many European subcultures which were once innovative are no longer so. Are Greece and Italy even mere shadows of what they once were? UK, Netherlands and France are doing somewhat better, but are nowhere near their erstwhile peak. The same is true for Germany and Russia, though less so..
In each case, a culture that could once innovate, in a given set of conditions, lost the ability to do so after those set of conditions changed. However, as I have previously said, civilizations and cultures are themselves mechanisms to preserve the status quo- often at all costs.
Therefore the real culprits behind declines are those who try to preserve and maintain traditions, mores and culture in the face of continuous, and objectively quantifiable, adverse feedback.