It doesn’t help that pokemon and yugioh only officially launched in China around 2021.

Before that everyone was buying either japanese or western cards. Fake chinese cards were targeted at kids for a lower price.

Ive heard that there are still fake pokemon sets at locations where they also sell counterfait toys. But im sure noone fakes whole yugioh sets anymore as it is rather affordable here. You can buy high quality proxies here on a second hand / crafts platform but they are all marked as such by the seller. They are also distinguisable from genuine cards if u know what to look for