My red flags?
1. If the title screen is unreadable in one way or another. If the title of the game is a made-up word or a super obscure word that is hard to pronounce or even understand (or has a made-up pronunciation). Thin red text in weird jagged lines on black is difficult to read (I know one game that did this, so it's my example) is another of those "unreadable" things. I always know I'm in for a pretty dull ride if the title and title screen are difficult to decipher.
2. Graphics look overly stylized. I'm all for fantastic graphics, but often I run into "okay, they spent all the time and money on graphics, so what did they skimp on?". Usually, it's the story/characters that have suffered, though it can also be that everything looks pretty and it's just a stock fighting system.
3. Vague descriptions. A proper description sets up the game and what to expect to be playing. Things like, "A funny adventure" don't tell me anything. Especially since humor is subjective personal opinion. Likewise, "action packed!" and other such phrases that are vague put red flags up. Likewise, "deep levels of customization" send red flags as well. Ideally, a game should be trying to sell itself on the experience and not its in-game features. I get wary when it starts advertising its features as a good reason to play a game. I don't play an RPG because it has "customization" and "crafting" and anything else. I'm playing an RPG because I want a good story. If the focus of the description is on anything except an interesting or unique story, red flags swing up all over the place.
4. Generic Storylines. "You are a hero, go kill the bad guy and rescue the princess to save the world!" I don't mind if that's the storyline... If it's presented well, or even in a new way. I choose books, anime, and even TV series this way as well. I want to see new things, or old things tackled in new ways. I don't want to play the same game as everyone else, I want to play something few people have played. I enjoy new experiences. Towards this end, I like the concept and writing of "You Are Not The Hero" even though I'm not a fan of the gameplay. I think it is altogether an interesting and fun concept with (in my opinion) some really good and solid writing. I don't want to give examples of "bad games", because I think it would be unfair to those who made those games, but an example of a game that meets my "new experience" criteria should be okay here.
5. Poor grammar and spelling. I will, usually, forgive a bit of poor grammar and spelling. I used to play fan translated games on emulators, and I do watch fan translated anime, so I am used to a fair measure of bad grammar and even spelling. It's especially expected if it's from someone who doesn't have English as their first language. However, I at least expect it to make some kind of semblance of sense. If the grammar and spelling are so bad that I can't understand what is going on, it's going to drag the game to grinding halt for me. Generally, it's a red flag for the game if we can't get through the first 10 sentences of dialogue without a mistake in every single one of those sentences. I'm lenient, but only to a point.
6. Greenlight. I've been burned by Greenlight a few times. I'm always skeptical when a game is greenlit. Especially considering the quality of games (and not just RPG Maker games) that come out of Steam Greenlight. There are exceptions to this rule, of course, but it is a pretty big red flag for me.
7. Overly strange openings. I know a lot of people like to start the player "in the middle of the story", but it's not something I enjoy mucking around with. Presumably, a good opening starts with fairly normal events to establish what is "the norm" for the world we are interacting with, and then strange things happen. Too many games open with "strange things happen" without establishing any kind of normalcy for the world we're in. How do I know getting sucked into a random portal in the park isn't something that happens every day? How do I know visions aren't just something people experience in this world? A lot of more recent anime have this problem as well. For me, it doesn't bode well. It doesn't usually pay off as a "good experience". You have to have some set-up, otherwise there's no context for the initial plot.
8. "Artsy" games. This ranges from games that beat you in the face with their metaphors or symbolism and try to be as "artsy" as possible. I don't mean "look good" either. I mean, being obtuse, abstract, and deliberately vague so as to appear as some sort of "artistic game". Games like "Dear Esther" fall into this category for me, as an example (It isn't RPG Maker, and I'm not fond of using actual RPG Maker examples for bad things, because it feels sort of like character assassination when the criticism wasn't actually asked for by the creator. However, games that actually made money that aren't RPG Maker... I consider that fair game for examples. Especially if they're on Steam.). I do not mind a game that has artistic value and merit in it. I mind when the entire point of the game is to be artistically valued and have artistic merit. Usually, it leads to a lot of navel gazing, exposition, and forced symbolism. What I mean is, it typically doesn't leave a player to come to their own conclusions and ideas and generally leads them around by the nose as if they were a dog and the creator were afraid the player may urinate on the carpet if they were left to think for themselves. It's a red flag for me.
That's all I got for now. I realize that's pretty long, but I hope I explained myself well.