In the end this is like banning fake news, you just can't.
I suggest people just take a credibility approach. As an example, I no longer bother with HN's "Who's hiring", everything there is bullshit.
Besides, job sites are just social media, their purpose is not to inform, it is to create eyeballs to advertisers. You should discard them, like you should also cancel Facebook, Twitter and WhatsApp.
replies(1):