The problem with crowning The Voyage Home as the best Star trek movie is that the Enterprise is absent.
It’s not like you need the Enterprise for good Star Trek. Many of the best episodes have not really used the ship. But for a movie to be the pinnacle of Star Trek in fan reactions, the absence of the Enterprise is keenly felt.
If I was going to put any movie up against The Wrath of Khan it would be the Undiscovered Country. Everything I like about TWoK returns in The Undiscovered Country. An iconic and interesting antagonist? Check. A starship battle decided by clever outthinking of the enemy instead of a situation where the main character and antagonist end up in punching match? Also check. Kirk confronting his place in a world that keeps passing him by? Also check.
If I had to ask why does TWoK beat out TUC, and it only does by the narrowest of margins, it’s that TWoK has slightly more universal themes. The Undiscovered Country is about the end of the Cold War, and if you grew up in that time, it resonates strongly. Treating your old enemy with respect, moving past your old hate, these are things which landed much harder in the early 1990s than the early 2020s.
But growing old, life passing you by, old mistakes coming back to haunt you, the danger of revenge, all those stand out today as well as they did when the movie first aired.
TWoK aged better than the others, though not by much. Many of the other movies are very, very good. I personally rank TUC and TWoK almost even.
I do think TWoK has in my mind soured a little for the same reason that First Contact did. Its success ensured we’d get so many attempts to dip into the same well again. But that’s a very subjective issue, and one which it’s hard to really hold against TWoK.
Let’s imagine the baby Gorn start off the way you describe, a perpetual small hunter that also produces more offspring. As they age they get bigger and stronger before they finally die.
The adults who take care of their offspring have an advantage over adults who do not care for their offspring, and possibly even more over the babies who never become adults.
There is another selection barrier as well. If all you have are baby gorn, what happens when you run out of hosts? This can easily happen if the hosts are over-hunted. If baby gorn pop out and there are no hosts, and they die out in a few years or even months, that’s an evolutionary dead end. The ones which can last a long time until new hosts are available will eventually be selected for.