You’re basically asking what I would like to see in a book. Because visual novels have more in common with books than with gameplay-oriented games.
To answer the question: when I read fiction purely for enjoyment, I usually read fantasy. Fantasy that takes its world seriously, not rpg-verse parodies or isekai power fantasies. Something along the lines of Lord of the Rings or The Earthsea cycle. With the added visuals of a visual novel, but without all of the compromises involved in a TV/movie adaption.
Wait, I just noticed that you’re one of those AI “developers”. I don’t want anything from you. I’m leaving my reply up in case someone else finds it interesting, but I’m blocking you now, so don’t bother responding.
there's a niche or two for VN's that aren't dating simulators
Visual novels are not dating simulators and dating simulators are not visual novels.
Dating simulators have a game play loop. They are actually more akin to a rpg. You typically have free roam and stat management. Inventory. Ressources. Your goal is just not to overthrow the big bad.
Visual novels are a branching story. On the extreme end there are kinetic novels, with no branching (basically a movie). There is complex visual novels, that almost have a game play loop, or hide the loop.
The concept is basically this https://en.wikipedia.org/wiki/Choose_Your_Own_Adventure and I assume, most or all those children books did not have romantic plots.
But since vn is about story, and stories about romance are very popular, of course a huge lot of vn will have that plot. And with a computer's capabilities, the genre often blurs into other genres, including rpg and dating sim. And of course a dating simulator with a few text dialogue boxes, will easily be labeld as visual novel, especially if you use a "vn engine" like renpy. But reading text in a computer game, does not make that game a visual novel. (And yes, I have even seen games be labeled point&click, because you had to click on things... I have opinions about tags ;-)
but I don't know where they lie
Anything that is exciting and anything that will get more exciting, if you can chose the branching. Adventure, fantasy, science fiction, road trips. Not stamp collecting. Although, there was this rather good stamping game, that had decision making and story telling, but not many would consider it a vn.
Since you tagged your game "action", maybe you are creating another type of game, and are only fixated on the visual novel label, because you used the renpy engine. A lot of games tell a story. And many games let you chose the outcome of the story in some way.
