Lately I've been watching TOS reaction videos, like these guys.
There's a fair bit of commentary on stuff that didn't age well: the unconvincing special effects (even though inevitably they're watching the enhanced version); the obvious use of stunt doubles (obvious on giant HD TVs, anyway); the mixed messages (Racism is bad but all Klingons are evil! Women are equal but also sex objects! Don't interfere in other cultures unless they're doing it wrong!); the clunky tag scenes capping off tragic events with a good laugh on the bridge; etc. And there's a lot of cluelessness about the cultural environment of the 1960s (Why is Chekov wearing that crazy wig and always saying stuff was invented in Russia?). But what stands out to me is how certain storytelling conventions that we didn't question in the 1960s and '70s really bother younger viewers. The most obvious example is the total reset, where events in previous episodes are rarely if ever mentioned again and don't seem to have any lasting impact on the characters. Also, the instant love interest, where a character forms a deep romantic attachment in just a few minutes of screen time.
These were conventions necessitated by practical and business considerations: episodes had to be accessible to new viewers; work as stand-alones; be completely wrapped up in an hour; make sense viewed in any order; not depend on actors to return for recurring roles when not under contract; consist of a teaser, 4 acts, and a tag; etc. I'd like to say that I accepted these conventions because I understood all those considerations, but I'd be lying. For one thing, I was just a kid, and for another, everyone, kids and adults, had so much less access back then to information about how media (and just about everything else) worked -- it's almost inconceivable today, even to those of us old enough to remember it.
I saw Star Trek in its first run just a couple of times (I was very little), but became an avid fan watching daily reruns in the early 70s. My peers and I were blissfully unaware of anything and everything behind the scenes. We knew shockingly little about how TV was made -- I was 12 when I started going to conventions and learned that scenes were shot out of order, sound effects were added later, actors didn't do their own fights, etc. The blooper reels were an entire education in TV production. We had no ability to watch anything other than what was broadcast in real time, and we never imagined watching any other way. We had culturally mediated expectations -- we just knew that TV tells stories in a certain way. (I suppose this is not unlike an ancient Greek audience that didn't question why an onstage chorus always spoke in unison, or an Elizabethan audience that didn't question why all the actors were male.) I realize that even now, knowing what I know, when I watch TOS I fall right back into the old mindset -- or at least, part of my brain does, while the other part, which has added decades of knowledge and experience, not to mention internet access, does a simultaneous running commentary. But even so, I can't relate to not "getting" the way old TV worked; it brings out the cranky old lady in me who wants to kick these kids off her TV lawn.
Anyway, speaking of the old conventions, here's some raw footage that found its way onto YouTube -- I believe I was actually somewhere in that room.