When there's a full-scale, bad-faith anti-China campaign in the media, doing leftist critique in a public forum only serves to aid the campaign. It doesn't sound like "communism can be better than Chinese communism" but rather like "even communists hate China".

You're right that Chapo should be criticizing China - it's secluded enough to not add to the propaganda. But I'm betting people just aren't personally interested in China enough to get into it. You have to know a subject intimately if you want to comment intelligently, not just repeat rumors.