You know, I’m the contrarian on this episode. I liked it, and I’ll tell you why.
As aliens in full costumes go, it wasn’t bad for it’s time. I had no trouble with its looks. I was a TOS fan from the early 70’s (wasnt’ quite born early enough for the original run), so I had no trouble with somewhat marginal effects anyway.
I thought the Gorn race was interesting and genuinely possible, unlike the weird xenomorph mash-up of the current Gorn. It’s not hard to imagine a strong but slow-ish lizard race, particularly if it was functioning in a cooler-than-normal environment. We don’t know how hot their native planet is, so it could have been operating in the equivalent of a Midwest winter.
I enjoyed Kirk being stripped of modern tech and having to depend on his wits to overcome a stronger, implacable opponent. That’s the essence of every TOS conflict anyway: They don’t gadget or technobabble their way out, they come up with clever or sneaky ways out.
The source of the conflict was morally ambiguous. The Federation was just doing their normal thing, but they accidentally built an outpost in an area the Gorn considered theirs. In this scenario, the Federation meant no harm, but you could see where a powerful foreign entity building bases in their territory could be seen at a dangerous threat to the Gorn. A far cry from the modern day Gorn that want to fucking EAT us.
Now, I don’t want to get off on a rant here, but I got grievances with the clown-show that is the modern-day Gorn, and I don’t see why I shouldn’t take this opportunity to subject you all to them. 
- How in the name of the Great Bird of the Galaxy does the modern Gorn make ANY goddamned sense as a species? They’re an intelligent, technological species that HATCH ON A PLANET AND ARE LEFT TO FEND FOR THEMSELVES? They’re just left to kill whatever they find, including indulging in cannibalism, all the while learning nothing of speech, writing, math, the empathy and cooperation that a functioning society requires to. . .well, BE a society and not a battle royale?
- And the adult Gorn, instead of populating said planet with a domesticated beast like Gorn cattle, or combative but easy-to-breed non-sentient creatures like Gorn dogs, cats, etc, seek out sentient, technological races to feed to their young, thus making them a target of EVERY OTHER SPACE-FARING RACE IN THE GALAXY?
- At some point, they come back to the planet, scoop up the unsocialized, cannibalistic little psychos, and begin to socialize them? Teach them language, cooperation, how to use technology and sit up straight at the table? HOW? They’re supposed to teach them all this while, somehow, not being eaten? What does a Gorn grade-school look like, with the teacher explaining multiplication tables whilst trying not to be eaten by a zerg rush of students?
- How were the Gorn race FIRST taught language, agriculture/animal husbandry, math, socialization, the wheel, fucking FIRE? Who was the first group to pick up the juvenile cannibals and teach them everything needed to live in a technological society? If this is their life cycle, how did this first group of sentient socialized Gorn develop while living on the last-Gorn-Standing planet, and then leave the planet?
They just didn’t try with this race. It can’t be a thing, it can’t ever have evolved to this point. It makes no logical sense. There’s a lot of info out there about Vulcans, Orions, Andorians, etc. Have they attempted to logic their way into how this race could have evolved in any reality?
Say what you want about the original Gorn species in, “The Arena”, they could actually have evolved into what we saw.