I happen to disagree with that assumption. The aforementioned cycle of "challenge and response", I believe, entails that cultures are often victims of their own success. If everthing is in order, stagnation follows. But stagnation itself is a weakness, which leads to problems (challenges) which then demand a dynamic response (or they kill you, if you fail to respond). China has seen periods of great challenges (war, fragmentation, upheavals of all sorts), all of which were overcome (by innovation and transformation), and led to subsequent periods of order (unification, peace, properity), all of which lead (in the long term) to stagnation. This happens to all cultures, everywhere, and is not somehow unique to China. Europeans simply ran into a China that was at the apogee of unified period, clearly going into stagnation. And so, European historians painted all of Chinese history in the light of that view.