I would say that portraying sex or oral sex doesn't have to be "jizzing on someone's face"
I can think of examples of tv or film where the sexual relationship was the story, and of course it's depictions were very germane to what's going on.
There is a film called "The War Zone". It was a film about a boy who winds up stumbling upon and learning of his sister's sexual relationship with their father. The depictions of sex in the film albeit incredibly difficult to watch was effective and important as to the impact it was having on her. I don't recommend watching it if you have sensitive sensibilities, I do and I wasn't prepared and it was difficult not only to watch but impossible to forget in all the wrong ways.
There are other films where a more positive sexual relationship is the story and depictions of it are tasteful and part of the story and wind up being fairly straightforward in their depiction of sex.
So I for one am not against the idea of sex in film or tv and don't view that in and of itself as a bad thing. However I am at a complete loss to imagine where sexual relationship would make a decent story for a trek episode in any way, let alone in a fashion where it's depiction would be part of or add to the story.