You are reading too much into it. TOS was never so serious, or so technical. There was like 3 episodes of TOS where they travel back in time to 20th century earth (convenient for viewers). Seems like they do it all the time, right? In fact, one episode (assignment earth?) is so ridiculous it just opens with the Enterprise already back in the 1960s and Shatner's voice over goes something like "we are on a routine time travel mission to further understand 1960s culture on earth..." or something like that. No further background is given. And the thrust of the episode involved a guy in a bad suit who has a magical black cat and a secret portal in the closet of his Washington office, and he accidentally abducts an I-Dream-of-Jeane counterculture ditz girl as his secretary, in a plot to sabotage a nuclear missle to teach humankind about the dangers of the nuclear Cold War.. And then at the very end of the episode you discover that the magical Black Cat is actually Elvira or something, but its only for one shot and its not really elaborated upon. The episode ends before the Enterprise even travels back to its own time, I guess we just assume that they know what they are doing since it was like the 2nd time in that season alone that they did it.
Yeah.
And you know what, its a pretty amusing episode. That was Star Trek.
So, if time travel is so fucking routine that the Federation sends the Enterprise on a casual mission to the 1960s to study American hippie culture, you'd think whenever there was any problem in the universe the could just hit that magical "undo" button by going back in time. Fuck Spock knowing it, by TOS it seems to a casual technology the entire Federation uses.
Again, the science in Star Trek never made sense, and none of the plots were ever consistent. The Boost had it right, there is this myth that TOS was this ponderous, perfect show, but it was a mainstream 1960s adventure program with karate-chopping captains and bellbottomed, beehived seductresses in every episode, with about half the episodes involving the crew trying to overcome some flamboyant trickster god or escaping from a world that ridiculously was exactly like earth in a certain historical period except for one crucial difference.
The JJ Abrams ST captured the spirit of TOS pretty perfectly. I think a lot of Trek fans these days just grew up with the 90s' Trek, which is pretty far removed from the corny, actiony, sexy, adventury Trek of the 1960s.