China does have a point that in northeastern China there is a large Korean minority group present that they were trying to represent during the opening ceremony:

South Korea plans to continue global efforts to publicize hanbok, the traditional Korean attire, as its signature culture, a government official said Sunday, as people here are in an uproar over China’s use of hanbok during the winter Olympics opening ceremony.
Korea Times
One woman clad in hanbok appeared among those representing 56 ethnic groups across China during the event held in Beijing last Friday.
You can read more at the link, but clearly the CCP was trying to stick it to the West and their diplomatic boycott of the Olympics over human rights abuses of the Uighurs. This ceremony was intended to make it look like all the ethnic groups in China are happy and content and the West is wrong about repression of minority groups. I doubt this had anything to do with stealing Korean culture.






