The EU can do the same thing and set up their own firewall if they wish to enforce GDPR on foreign websites.

The fact that their citizens would revolt over the idea of internet censorship, is irrelevant. The point I'm trying to make is that EU saying "you can't serve X to our citizens" and China saying "you can't serve Y to our citizens" is no different and it's upto them to enforce it within their borders if they wish. The EU doesn't get to play world police any more than China's government does.

FWIW baidu.com and tencent.com are both pretty damn GDPR incompliant and the EU isn't doing anything about it. And yes there are Chinese-speaking EU nationals that use these companies' services.