Emily's Cat
Rarely prone to hissy-fits
It's kind of a strange remnant of a previous time, sex specific acting awards. Men and women have no innate differences when it comes to acting ability.
You're missing (or handwaving away) the reason those separate awards exist in the first place.
There is no innate difference in acting ability on the basis of sex. But there IS a difference in the number of leading roles available on the basis of sex. There are still many more male leading roles than there are female. And the biggest grossing films are still those that feature a male lead.
Having an award for best actress encourages customers to view more films featuring female characters and also encourages writers and filmmaker to develop female roles to be more representative and less stereotyped.