TOS definitely had it at the most balanced and thoughtful, even if Kirk readily disregarded it because it was all about appeasing his ego (e.g. "The apple").
TNG... oh sheesh. From "Justice", as filmed, exploring the ludicrous extremes of it, to "Code of Honor" where Picard flagrantly disregards it and for reasons even Kirk would be embarrassed about... then comes "Pen Pals", which is surprisingly thoughtful - but, as with a lot of season 2, introduces concepts that become too much a crutch later on. Not to mention season 5's almost completely cringeworthy "The Masterpiece Society", which feels like a rebuttal to "Pen Pals", only this time they slather on the maudlin shit and how this colony, whose structure is asinine to begin with, is now said to have been better off destroyed than via their holier-than-all interference. Ugh. At least it had a great Geordi scene making up for it, in the most unsung of ironies once you think about it. So it's not as much "cringeworthy" but "highly contrived" in setting up the story for one specific mindset, which is rather typical of season 5's soapbox mentality, even if - soapbox or not - it still gets audiences to think - in one direction or another. All I know is, "Pen Pals" still feels more entertaining as a whole story, and "Masterpiece" doesn't hold up much beyond a couple set piece scenes.. YMMV.
VOY flip flops on the issue more times than a bunch of fish that are on the floor thanks to Mittens the kitten knocking over the tank with an impressive amount of strength that very few kittens can manage to muster.
DS9 was set next door to a wormhole and a tidy little war, which turned the whole idea into beautiful grayscale since, as with everything else, no simple plot button could end the story as neatly as any given episode of "The Brady Bunch", though that episode where Greg's friend puts his ciggies into Greg's pocket and Greg is all like "I'm going to prove myself" and the kid who put the ciggies there confesses and all is well right at the episode's end, and the actor playing the ciggie kid also is the lead kid in season 3's all-time classic "And The Children Shall Lead"... Craig Huxley did a decent job with what he was given, in both shows, and he did invent a musical instrument that was instrumental to Jerry Goldsmith in "Star Trek The Motion Picture" that's rather quite good and scaled well to the threat of V'Ger...
Yeah, the Prime DIrective is just there like plot fodder. Like that light fixture store that's full of cool switches you can turn on and off. Have enough rows and columns of lights and you can configure the array to say a dirty word, since a whole sentence requires more fixtures than would ever begin to be on display... silly 8x8 grids and all...