MMO - I like multiplayer games just fine, but whenever they call it “massively” multiplayer, I know it’s going to be a grindy time-sink with anemic gameplay and the requirement to join some sort of group of other players in order to progress. It’s one of the few things I have filtered on Steam because it’s a guaranteed hard pass every time.
Turn-based - This one is hard for me to admit because I’ve played lots of great turn-based games and will inevitably play more of them, but for some reason when turn-based is a key feature, my brain interprets it as being a low-budget and/or low-effort game, or that the gameplay won’t match how the game is presented. It’s not that I dislike the concept of turn-based play, but when I see “turn-based” in a description I just glaze over.
Early Access - I don’t dislike early access, but the fact that it has no specific definition bothers me a lot. There’s no way for me to tell whether the game is a complete enough experience to be worth starting, so I usually end up passing until the game gets a full release (which isn’t a bad thing, but it does mean that early access is an automatic red flag.)
There are certain genres that I’m not that interested in, like puzzle games, visual novels, hardcore simulation games, etc., but the above are things that make me think twice about a game even if it looks interesting otherwise.