Look back on history, though China had the most powerful navy and army since the 10th century, we did not want to conquer the whole world. Only the whites would go all around the world robbing and killing.
I'm not Chinese. Not remotely so. I do, however, know for a fact that China was practicing an active policy of imperialism until fairly recently in modern history. The emperor (take note of the term) fancied himself sovereign of a global dominion which included Europe, as dynastic literature tells us, and with the exception of a brief period of isolation during the 16th and 17th centuries China was as imperialist as they come.
Prosperity of China is indeed great. At least we would not turn into another superpower that invades another country thousands of miles away.
Perhaps because you're too busy oppressing your own people.