. . . The miniskirts were basically there to sexualize the female characters in TOS and early TNG. Extending that to male characters doesn't make for egalitarianism, it just extends the objectification.
If they wanted to do something with draped fashions as part of 24th Century Federation culture, that would be valid, but they'd need to give it context. The only context we the audience saw was the pre-existing objectification of women in the miniskirt uniforms. (Which is gross in its own right -- imagine the outcry if the United States Navy were to start requiring its female sailors and officers to wear short miniskirts as part of their uniforms. People would rightly be outraged.)
Remember, though, that in the popular culture of the late 1960s, the miniskirt was seen as symbolic of social and sexual
liberation for women, like the short flapper dresses of the 1920s.
Yes and no. On the one hand, yes, it was an act of sexual liberation to move away from the complete suppression of female sexuality. But almost as soon as things like that began to happen, they were being appropriated by patriarchal interests; women were allowed to be sexual, but only in the context of objectification and subservience to men. Second-wave feminism was really only just getting underway when TOS began, after all, and the U.S. still essentially operated under a system of unofficial gender apartheid.
This is reflected even in TOS, which parroted the sexist assumptions about women's roles of the 1960s mainstream America. Pike in "The Cage" notes that he feels uncomfortable with women on the bridge except for Number One, indicating that Number One is an outlier and it's extremely uncommon for women to serve on starships -- reflecting a production assumption that the then yet-unnamed space service on
Star Trek would be male-dominated and sexually discriminatory, like the U.S. Armed Forces. Women seen throughout TOS mostly hold support positions -- communications operator (telephone girl), nurse, and star-struck love interest. It's even explicitly stated that women cannot become starship commanders in the TOS series finale. Don Draper would have been completely at home aboard Kirk's
Enterprise.
And the miniskirts played into that. Yes, there was a notion of sexual liberation at work, but it was appropriated for male pleasure; TOS is
full of the male gaze. Even that limited form of liberation from women only occurs in the context of serving a male interest.
And, no, the fact that William Shatner's shirt came off a lot does not equal things out. Being seen as muscley and macho is itself a male power fantasy; Kirk's shirt getting ripped off plays into heterosexual male power fantasies about what a real man is like.
All that's speaking from a real-world standpoint, of course. Speaking in-universe, even if we retcon things to try to establish more gender equality in the 2260s Federation Starfleet, it's still a ridiculous thing to have miniskirted uniforms. It opens the door up to all sorts of problems with sexual harassment --
especially if the miniskirt is mandated. The best we can do to retcon the skirts to make them less objectionable is to assume that they're optional. This seems to be the assumption used when the miniskirts were revived for ST09, since we see female Starfleet officers with full sleeves and pants rather than just the skirts.