Well, forgive me for saying so, but sexism in space is just a stupid argument. Empire couldn’t have any sexist agenda. Only reason why there isn’t many female actresses around is because it was made in the 70’s. Trying to find a in lore explanation for the lack of females in the movies is just pointless. There isn’t many because they didn’t hire many female actresses. They didn’t hire many female actresses because it was the 70’s.
Also to be fair, 99% of the Storm Troopers never talk and all of them are wearing full body armor and helmet, there is no way to determine their gender. Sure, we never see a female officer, but there is no way to say there wasn’t female officers, we never saw all officers. I know that doesn’t sound like it is a great argument, but it was never stated in the movies either way. There is no way to determine one way or another. (I am sure Ady could add a few female Empire officers and a few female Rebels in the edit and to be fair, it would be a brilliant addition, but depending on the difficulty, it might not even worth it. Not to mention these added people wouldn’t be able to speak because adding extra lines would alter the movies too greatly unless it is done in a extremely calculated way.)
We don’t see any female Jedi or Sith in the movies either, does this mean there were no female Jedi or Sith ever? Ignoring the later movies, we never even saw Leia use any Jedi powers, so one could argue maybe being a Jedi is a male thing. You will notice neither argument holds any facts. We are just assuming because of what we see in OT.