Why do you think China has a capitalist economy? Because it is thriving? It is indeed! But this is unrelated to capitalism. Capitalism is not economy good and international market access, socialism share potato and live happily.

Capitalism is the control of means of production by a few individuals and exploitation of the workers enabled by this private possession. In China, the small and medium companies are allowed to be private but the bigger companies or the ones in critical fields are nationalized. Something like 80% of investment firms are public as well

You can read more on this wiki: en.prolewiki.org/wiki/People's_Republic_of_China