Which is worse?
People who complain about games they have never played, or people who try to give advice on games that they never played?
Depending on how the advice is framed and how much I know about the game, I think the complaining is worse.
If I'm playing a new game and trying to figure something out, I don't mind if someone is also mildly trying to figure it out, too. Like things like "hmm, do you have a journal?" or "was there a town you missed?" But if it's straight backseating like "you missed that" and "no, you shouldn't play that - I heard it's stupid. play something else" - that's not wanted at all.
I'm tired of folks complaining about games they've never played or haven't even come out yet. Like don't poo-poo on something that other people might be interested in. Don't make them feel bad about being interested in something you're not, y'know? We don't need more negativity in the gaming world.