Honestly I personally do not hate the fact that RO's are gender selectable, but I do hate how Nicky implements it.
Except for Ai, the gender of the RO's does not play a major role in their story or arcs as far as we've seen. And since in a cultivation world the limits of female to male bodily strength very quickly becomes a non-factor, it doesn't matter if they are male or female.
Now I am assuming here of course, because who knows what Nicki has planned for the characters, but the best example of my point is Ruo. No one hates on FemRuo because he/she behaves almost entirely the same regardless of the gender selected, and we all know it's basically to comply with the laws of Russia while giving the players a RO regardless if they play male or female. I remember when gay romances were still a thing in the beginning so it's not like Nicki himself particularly cares.
The problem is how Nicki implements it. The reason why no one complains about FemRuo is exactly the same reason as to why people don't like the others being gender-selectable. For Ruo it makes sense as to why he/she would act almost exactly the same way—to this character their gender is not important at all. But if Caihong, Tigress (not saying Tiger) or Heavens forbid—Ai, become gender selectable and still act the same, it will ruin their characters. Tigress and Caihong are more or less designed to be female and it's pretty visible, and Ai's whole character would not make sense if she was a man, because then instead of a slut he would be called the stud, and his issues would be the other way around. A "suffering from success" type of character.
Now after Nicki finishes the story and adds most of the features, it would be sensible to dedicate some time to that, because by then the story would be clear as to whether the gender is important or not. But right now it just feels like an unnecessary thing that he just slaps on there for variety's sake.