China has always absorbed other people into our culture, sometimes not even on purpose. Even conquerors get absorbed. The heirs of Genghis Khan, the Scourge of Heaven, assimilated into Chinese culture within a couple generations. Xianbei, Khitan, Manchu, etc. The Khitans, despite warring against China on and off for over a hundred years, immediately declared itself the Liao dynasty, adopted the Chinese legal system, folk religion and invented a very Chinese inspired writing system (which to me looks like an AI hallucination of Hanzi) as soon as they secured a kingdom.

There was a period of time after the fall of the Ming when the Korean Chosun dynasty referred to itself as "소중화" (lit. Little China) because they considered themselves to be more Chinese than the Manchu. There was a Korean Emperor who was Chinamaxxing in the 1600's.