I agree; but it was no accident that the Original Series was "like" a western in space. That's exactly how Roddenberry intended it to be.

Look at his prior credits and those of several of his actors:
Roddenberry: "The Virginian" 1 episode, "Have Gun, Will Travel" 23 episodes, "Whiplash", "Wrangler"...
DeForest Kelley: "Death Valley Days", "Laredo", "Bonanza" ...
The same for James Doohan, Leonard Nimoy, and William Shatner.
It looks like most, if not all of them worked on "The Virginian" together.

To me, that's part of its charm: "Wagon Train" in space.