Even if they exaggerate about being fans, they completely miss their job description if they have no idea about the backgrounds and history of the game they are supposed to be (p)reviewing. It's part of a journalist's homework to know what they are talking about. Most of these "journalists" so far don't even seem to know what turn-based combat is.
Of course they're fed propaganda by the devs. The important thing is that they are supposed to be aware of that fact and judge the propaganda accordingly. If ten angry guys on a website can figure out what's wrong with a game judging by the propaganda alone, claiming that proper journalists couldn't possibly see anything negative in it because it's all dressed up like a Taiwanese prostitute is downright ridiculous.
Reviews and previews alike need to be balanced. You can't judge a game by its pre-release propaganda, but that doesn't mean you can't say anything negative about it — if you can praise it, you can criticise it as well. They already DO judge it — positively, to be specific — so don't start with that bullshit about neutrality.
The problem with game journalists is that they aren't. They don't get paid to criticise, they get paid to advertise. If they wouldn't give positive reviews to the big companies' products, they wouldn't get anything to review, which means they lose their advantage which they need in order to compete with other "game journalists". It's the game journalists that rely on the game companies, not the other way around — there's just too much demand for first looks and exclusive previews and too much supply of "journalists" willing to sell their credibility in order to get those goodies before anyone else does.
Plus, who wants to read about bad games anyway? The usual target audience of the mainstream market wants instant gratification now. They honestly don't care about anything beyond pretty explosions and twitch action gameplay. They don't want to know about how boring the story is or how inconsistent.
Why bother writing about depth or dialogues when your readership only cares about how many chances it gets to blow up a rat with mini-nukes?