China literally calls itself Middle Country (Zhong Guo)... they were/are the center of their universe, LOL. Impassable mountains to the west, the biggest and toughest ocean to the east, the Mongols to the north (they learned that harsh lesson enough times to stop trying), and untamed jungles and little worth conquering to the south. They had no place to expand to for centuries, no a reason to try.
Exactly, Zhong Guo (中國)and also Tian Xia (天下) everything under heaven.
They were everything. They didn't care about expanding or dominating foreign lands or cultures.