I think part of the problem with harem games is they give every girl exactly one kink, or she is there to represent an aesthetic, and most of those are pretty vanilla. So you'll have one girl that likes oral more than the rest, one that's into anal, the one with curly red hair, etc. The cast gets bloated to cover all the bases and none of the characters get enough screen time to properly develop. A smaller cast where all the girls are into several things would help a lot. You could write a very forward masochistic redhead with a thing for exhibitionism, but most devs instead create one slutty girl, one masochist, one redhead, and one exhibitionist, each with a quarter of the screen time and a tenth of the character development of putting all those kinks on one package.