ok my attempt to play this game has led me to 3 conclusions
First killer artwork for all except the chubby girl, she look's like you basically mixed a chubby and skinny girl together. honestly chubby is not my cup of tea but I think you might want to rework her. Also your orgasm faces need a bit of tweaking look more like elderly versions of the girls instead of grimacing into orgasm face.
Second yes too grindy with no direction. I can understand trying to open word it but no idea who what or how to get from point a to b for certain characters.
Third your sex scenes while nice need something. I would add either inner dialog of main character or narration style over position of the ongoing act.