Okay, worst things in Adult games:
- Dream scenes - they serve ONE purpose only: Delay the action. Noone that gets immersed in a story can find these "hot". It's not real, and has no heart to it. That's like jacking off to still images that have no context.
- Night scenes - Pulling off covers, touching tits, rubbing dick all over the mom's feet or whatever. Takes so much work for all the different renders etc. that could be invested elsewhere.
- Incest in general is so overused. Mom / Sister finding out MC has that huge fucking cock by accidentally seeing it and then getting all hot and bothered, unable to stop thinking about it. Then it takes 6 or more updates until anything of importance happens.
In my opinion, if you want to put in incest, the "freshest" approach you can take is to have the characters be naturally attracted to each other from the get go. There's no realistic approach, no sane person will fuck his parents or vice versa. Even if I hate the game itself, Midnight City pulls that stuff off pretty well imo.
- Highschool settings. No need to explain, I think.
- The [put in playful descriptive word here] girl/woman. Here's sporty girl with short hair. This is stern career girl wearing a suit and tied up hair. This is shy library girl with braids and round glasses. You catch my drift. Stereotypes are boring and their characters are never really developed beyond what fits their description. Make them complex, but not pretentious. They need to have motives, goals, reasons. I think 'Connected' has a very well written and unique female best friend / love interest. Where it all began and BaDIK also have strong characters.
- The 'slow burn' as people romantically call porn games that just artificially drag on without ever giving the fans / your potential customers/supporters what they're here for.
- If you value your story, you detach from it. The narrator chiming in every 5 minutes going "Ayoo guys it's me, Narrator, for a funny skit"
- Long ass tutorials one after the other holding the player hostage for 20 minutes before we get to know anything about the story.
- Grinding stats or money for hours. If I have to ctrl through the same slowly loading animations or renders 3 times a day ingame for 7 days to get new animations, I get turned off. It's tedious and adds no value, other than steal time.
- The MC is alone, and and if he has a friend, it's a fucking idiot. Obviously as I'm a pretty immersive player, I don't want to watch 'another dude' having sex, but I think a well written support character / friend is a good thing. If you played Acting Lessons, Liam is one hell of a good fucking side character. He was very, VERY popular and people were invested in him. He posed no threat to the MC, but he wasn't an asexual herbivore either. Same goes for the mohawk guy from 'Become a Rock Star'.
- Japanese logic and names, settings. Why do western game developers get off on naming their characters Ayame, Kanako, Takeshi etc. So many people probably watched tons of anime and forgot how real people are called and how they act.
But the most important thing I really want to say is this: I don't think you can avoid all the tropes. Everything is a trope now, you can't be completely original, ever. So don't feel bad when you make use of one if it fits the vision of your story.