This was a solid episode. It was good to see McCoy as the focus of a woman's attention rather than Kirk.
It was clear they consciously made the change up to try to avoid the notion that Kirk was just trolling for booty around the galaxy.
And I suppose, it made it easy that these guys were relatively confirmed bachelors - McCoy and Scotty, particularly, in their-mid 40s with no attachments.
And, production-wise, we don't even know that Spock is married yet. All we know is that he had somewhat of a dalliance with a human gal at one point. We know that Kirk is a hound with somewhat of a reputation in Starfleet.
The aliens were also well done. They could have easily come off as cartoonish, but Maab and Eleen were interesting characters.
I agree and I strongly believe that elements of this particular race were incorporated into the TNG/DS9 Klingon post-advent "revision" - watching this episode (which also, coincidentally includes a Klingon) makes it extremely clear. The Klingon could almost have been a Ferengi next to the Capellans.
Of course, I have no link or reference to support this - just a hunch. Whoever was tasked on revising/updating the Klingons would have, at least, reviewed all the TOS episodes containing Klingons, wouldn't they? So, it at least makes sense.
"Say to yourself, the child is mine. The child is mine. It is mine!"
"Yes, it's yours.'"
One of the best punchlines by a guest in all of TOS.