TOS isn't my favourite Star Trek but something about the tone of the first season sticks with me in a way none of the Berman-era stuff does - space feels totally unknowable and unreal, and the ship feels almost like a floating theater stage that's drifting from one mythic morality play to another.
I like some of the Berman-era worldbuilding and more consistent political factions, and the quadrant model that lets writers place stories at certain points in the galaxy, but I think on the whole I prefer TOS' method of deliberately having almost no internal logic so that space just becomes a terrifying nightmare that's swallowed the ship whole, and the crew are less like "real" people and more like symbols of humanity set against a universe that seems almost designed to test them at every turn.
