I know that feel. Imagine reading relaxed through some ok story between good sex scenes and suddenly being interrupted by some reaction based or time limited mini game. Just awful. I don't like it.
Sex > story. Obviously just a series of sex scenes would be pretty blunt. A little story to lead from one sex scene to another is perfectly fine. It's the better alternative to a great story between bad sex scenes. If you don't have to go for one or the other the true answer is obviously both...
My first NSFW game was Sex Games on my C64. On PC it was Polygon Love 2 with Loli Mod. It's basically a hydraulics simulation where you dress/undress your selected loli, put her in different poses on a selected scene and can move the camera around during the scene.
Porn games should be about porn. Story is fine. Grind is not because I need my hands somewhere else. Riddles also are not because I need to use my energy on something else but definitely not my brain.