The whole “the time line has been changed and we need to restore it!” shtick has been so done and overdone that it is indeed unusual that such an episode made it on my list (though of course Yesteryear has that same plot hook). Indeed I did not include City on the Edge of Forever, despite its hallowed status as the best in all of TOS, because the trope has been so overdone. Also I never bought that Kirk would fall as hard as he did for Edith Keeler – she’s too much of a Mary Sue for him. (“Listen, kiddo, Jim Kirk was many things but he was never a Boy Scout.”)
But this one works, and it works brilliantly. Great Guinan stuff, great Tasha stuff, and introduction of Worf’s fondness for prune juice. This battle where Picard says “That’ll be the day” – while unimpressive visually by today’s standards – is nonetheless the best action scene from TNG.