In the early '90s when I was first exposed to the Legends EU, the Empire’s racism and sexism was EU canon at the very least. Bear in mind the significance of Grand Admiral Thrawn’s elevated rank being even more amazing, as he was the non-human to earn the Emperor’s respect and achieve such a high status. The “Declaration of Rebellion” furthered this as EU canon.

https://starwars.fandom.com/wiki/Declaration_of_Rebellion/Legends

And remember, there are no aliens in the OT films within the Imperial hierarchy. I believe this was likely a subtle allusion to the evils and racism of Naziism. This was picked up on and expanded upon in the EU to include sexism.
Admiral Daala, whom I consider something of a Thrawn ripoff, was the highest-ranking female within the Empire.

https://starwars.fandom.com/wiki/Natasi_Daala

A lot of this was clearly eliminated with the coming forth of the prequels and Palpatine’s alien and female advisors…

…but I believe many of the time interpreted the Empire as a racist, sexist regime.

That’s not to say they wouldn’t necessarily use women in a lowly role as cannon fodder, but I am largely in agreement with ray_afraid’s appraisal of the Empire’s bigotry, at least taking into account only pre-1999 material.