I agree humans, on a basic level, are motivated by sexual desires (even if unconsciously). I also think, however, that we can and do build moral frameworks to improve our own well being which, in many ways, counter balance our more primitive impulses. We have concepts like the NAP which protect life and property. I think we have similar perspectives about sexuality and the role in plays in our power dynamics. I don't argue that we are fundamentally different than other animals, but I do think we have have a pretty high neuron count which has impacted our perspectives on this stuff as a social species.
You make a really good point about creating future humans. If sex is less important for that in the future, these dynamics will change significantly.