I don't think that justifies sexism.
So Nichelle Nichols and Grace Lee Whitney were sexist toward themselves?
You may or may not realize this, but both actresses have said THEY asked Roddenberry to dump the unisex uniforms that had been selected for TOS in favor of what they ended up wearing.
Miniskirts were a sign of a liberated woman in the 60's.
And no, they aren't "realistic". Neither is day-glow color coding for different branches of service.
Or FTL.
Or Time Travel.
If I want realism I'll go outside. Or watch people blowing each other up on the news.
Star Trek is science fiction adventure in the vein of Barsoom, Flash Gordon and Buck Rogers.
It's got green-skinned pheremone-emitting sex-slaves and touch-telepaths and energy aliens who feed on anger.
It was NEVER hard sci-fi nor has it ever shown the slightest inclination toward a realistic depiction of well... anything really but I think, given the way folks dressed on TOS, you could list realistic FASHION near the top of that list right along side science.
And some of us like it that way.