Humor is not a bad thing to add, as long as it's a good one. It also depends on your theme. If the plot doesnt take itself seriously, go nuts with it.
AI art is never a bad thing imo. It helps people who has low affinity in art.You just need to be good at making prompts .
Personally, I prefer the ones that doesnt have a realistic shading in them. Keeping the shading simple is the key.
Bad endings should always be the meat of your ntr game. You can add a good ending/vanilla route but imo, if it's something very cliche, I wont be bothered checking it out.
Goodluck in making your game.