what instantly turns you off from a game, outside of the obvious stuff like authorial bigotry?
Hmmm, interesting question.
I get turned off really easily and looking at what does it and why is a specific thing. Like I dropped Moonring like a hot potato, but it wasn't because it turned me off; it's because the game overwhelmed me. I would never bother telling anyone not to play Moonring because I didn't play it. So turning someone off feels like a specific introduction of a negative preference.
And it's not enough that I hate something about a game. I really hate how Control plays, but I haven't thrown it out yet because I am interested enough in what it's doing and how it's doing it in all the ways that don't involve playing the game. Signalis hard walled me on the first boss until I found you could adjust the difficulty, and by that point, the wall had sapped my enthusiasm for the game.
For TTRPGs, one thing that instantly turns me off is a condescending tone about D&D. Like, there's a small body of indie creatives who seem to think what they should do with my attention on their work is to complain about a game I'm not looking at right now, and that always projects a lack of confidence. Fortunately, I can't remember any of the games I've seen do this by name.
Kickstarter editions with giant piles of pieces turn me off; my table space and house space isn't infinite. A game like Too Many Bones requires, essentially, a closet unto itself. There's no way it's that good.
There's also this weird kind of incompetence that bugs me. Nier Automata is probably quite a good game, but it seems to want to talk 'about games' and then presents a really weird, unpleasant to play game, which means I'm left wondering why I should care whatever that game has to say about games. See also Doki Doki Literature Club, which is mostly just an OLEVN version of a type of VN that's been happening for decades, but people who've never been aware of what VNs are doing thought it was new and shocking. I guess I put Undertale in the same space, as a game full of absolute arseholes presents itself as a goofy uwu hey why do you care so much, hey why don't you care enough kind of thing, which just leaves me as an audience member wondering why the fuck I should listen to it.
Also if your game actively tries to remind me of a much better game, it's going to be rough. Thimbleweed Park and The Sam and Max Episodes both tried to evoke other games that I've replayed recently and which I think are really properly good, and the comparison just made it hard to put up with the weaker followup.