I'm glad that you gave them some feedback to how they could put the game out towards an audience with your similar interests but I still don't understand how the characters are irredeemable and broken, they're just characters in a VN and relatively common ones too. And I have to agree that contacting the game dev's and creators through itch isn't a bad idea, but they do have a twitter page and the dev's themselves have their own separate pages too. If you do really feel the need to reach out to them Id start with their Twitter page linked in the games description on this page.
Totally understandable, I get the no Twitter or Instagram thing as I am also a person who either doesn't check it often enough to really have the need to use it, or just don't like some of the toxicity it can cause in daily life. As well as the dating the types thing, it would be hard to play a game with the same types of characters you had dated previously but I don't think that's really the games fault for picking them as they're pretty common characteristics in these Visual Novels and are more desirable making the game have more of a hook on the people who do want those qualities.