I think I agree with you. I would go as far as saying this is true for everything, not only for science. I think we need to have categories to be able to grasp complex problem. And almost all of the time, those categories are arbitrary and only useful at specific scales and in specific context. It is the only way to think about large scale problems, just because we cannot handle every individual information in too large quantities.

Those categories are always “wrong” in some sense, but can be “useful” to understand our world. And I agree with you, at individual level, in our society, for sure sex at an individual level is not only useless but harmful.

Sorry, I recognize my position was unclear and could be taken for quite essentialist. Hope this clarify my position.