My thoughts on the game:
- I would say the game first and foremost needs a proper introduction. Spend a few screens introducing the background story and the characters. Who are they, why are they driving around in this van, etc. If there is no background story and character development, people will hardly become emotionally attached to the characters and just click through the game for lewd scenes.
- As for the lewd scenes, you made one thing right... you didn't just jump right into fucking. There should be a buildup of tension, teasing and corruption. Make people invest effort (but not just grind mindlessly) to get into the juicier stuff. Once they all fuck with each other, the remaining lifetime of your game will be limited. Characters can ofc still have sex with NPCs / side kicks to keep things lewd enough to keep people invested.
- Try to be somewhat consistent with the porn actresses and your characters. It's difficult but how would you expect people to get immersed in the game and its' characters if your Mom/Sister keeps changing hair colour, face, boob size etc etc. This consistency is imho one major element of what separates the very good games from the average ones.
- Try to allow people to rename the characters, this helps immersion. Ask other devs for guidance how to code it if required.
- Try to use Mom and Dad consistently instead of their names. It will increase the family atmosphere you go for. Should you go for Patreon, you need to switch those to caretaker or so due to their policy but create a family patch here.
- I had two code errors with crashes when trying to explore the suburbs and the abandoned house.Also I didn't identify a possibility to save the game before exploring a new area.