I didn't think it would be possible to make sex sound like it wasn't fun but... this approach to sex sounds boring.
Might as well complain that the average game seems to sidetrack the issue of "eating", whereas with proper thought about the gameplay we could have a wonderful cooking simulator that involved whipping cream, battering up fish, and smoothly spreading thick bechamel sauce over meaty lasagna.
And then onto the actual eating, where you have to find your mouth with your fork, while maintaing eye contact with whoever you're talking to. And then move your jaws in a manner that will grind down the food, but without applying too much pressure to the teeth or the food, and keeping the tongue out of the way of the teeth. With force feedback. And a health bar for the food, teeth and tongue. And the ability to squirt saliva so that the food get mushier. And then a timing mechanism for swallowing, allowing you to get the food down the right hole.
Frankly, I don't want a mature approach to sex from games. I want a mature approach to people and relationships. The rest is just organics.