O.K., back in the day....
....For a kid growing up in the 60's, when TOS first started airing the only roughly comparable television show would have been "Lost in Space." I believe that started a year or two before TOS. That is, a tv series involving "high adventure in space." [Rodenberry claimed CBS ripped him off by using some of his ideas for Lost in Space from a pitch meeting they'd had with him.]
So, you have to remember what it was like for us kids (at the time), we're watching Lost in Space.
Then Star Trek comes on and it's night and day in terms of the sophistication level and special effects.
I can't say I remember very much at all from way back then, but one thing I do remember, distinctly, is watching the very first broadcast episode of Star Trek. That one was "The Man trap" [salt creature episode].
I remember the climactic scene where the salt creature is disguised as Bones's ex-girlfriend and is sucking Kirk's salt out of his face while he sits there helpless & screaming. I believe at that point Spock had been incapacitated by the creature.
So Bones comes in, and "Nancy" turns around and looks at Bones and you see the reveal as "Nancy" turns into the disgusting loathsome salt creature, fortunately, Bones phasers it to death. After an uncomfortably excessively long amount of hesitation.
That "reveal" was shocking and freaked me out, I would say at least to a kid it was worthy of the most gruesome twists of any Outer Limits or Twilight Zone.
Of course at the time I didn't get all the Freudian aspects of that "sucking" creature, vagina dentata, etc. but it was still really really disturbing.
So that made a huge impact on me.
Then of course every so often it would go into syndication/strip reruns so at various points over the years I would get into watching the episodes again.
The original broadcast run also pretty much coincided with the Apollo program so you could say they reinforced each other at least in terms of a 60's kid's sense of the zeitgeist.
** In reference to "Elan of Troius" the biggest impression that made on me was the camel toe. Sorry but it's true.