I'm a big TOs fan, its my favorite series, but its use of sexuality was pretty base and blatant. The disparity in the costume choices for most of the male and female characters was quite intentional. They served no purpose other than to expose as much female flesh as possible. And as 1960s TV goes, only Laugh-In came close to the exposing that much flesh. (and most of that was Goldie Hawn) Though I guess the fans of male flesh could always wait for Kirk's shirt to be ripped or discarded. There is a great screen cap used in a caption contest recently of Kirk sauntering through the corridors, boots in hand and his shirt draped over his shoulders, his naked torso gleaming. It didnt really further the plot, but I'm sure someone got a kick out of it. I know those of us in the Caption Contest had fun with it.
TOS was no stranger to heavy handed, on the nose morality lessons. Even the the 1960s we could hear the anvil being moved into position and just waited for it to be dropped. On occasion TOS did rise above the usual pat endings. "City On the Edge of Forever" has one the best endings in episodic television. Shatner's delivery of that final line was perfect. Anyone who claims he's a bad actor need to watch that scene.
I think Star Trek can work in any type of storytelling format. And it has. Its been successful in the episodic and serial TV formats, as an animated half hour, in books and on the big screen. While TOS didn't use the serial format, it was no stranger to "Soap Opera" elements. They just paired it down to a single episode rather than spreading it out over the length of the series. I love TOS to death, but it was never on the level of Hill Street Blues, but I still like it more that Hill Steet Blues.
DS9 is my number two favorite Trek (hence the screen name) but I have to say I like the ENT characters a little bit more. Not sure why. They seem more relatable perhaps. It dont think T'pol ever stopped being a Vulcan. She was on a journey that explored what it meant to be a Vulcan and to examine that she had to step away. There were a few missteps along the way to be sure. I found her journey to be in keeping with what we know of Vulcans.
NO incarnation of Trek will ever equal or surpass TOS in my eyes. Not even DS9. There is something about TOS and it's characters that touch me in away that the other shows didn't. But I'm a first generation fan. I watched it in glorious black and white, first run using rabbit ears. Call it nostalgia if you like, but none of the spin offs come close. DS9 as I said is second, but it is a distant second. Then ENT, followed by TNG. Finally that other show.