I li9ke "Archons" for two reasons:
1) It's got a really creepy atmosphere at times. The scenes of Kirk and crew being set upon by the relentless locals are kinda like a zombie movie and IMO the backlot shooting sells it even more.
Also, it does better than most episodes the idea of presenting a planet with an actual culture. There's a bunch of pieces that are not
explained neatly and squared away, because Our Heroes don't have the time to investigate them and because the locals don't go volunteering explanations that they have no reason to think our Heroes need to hear.
The Festival is an excellent case in point: it's obviously important to the culture, but, why? Spock makes one conjecture, and we can make others, but none of them gets confirmed or refuted.
There's also the not-exactly-fitting mix of sets, from the Generic American City backdrop set (with apartments that more or less fit the early-20th-century design) and dungeons and then the high-tech(?) centers for processing and of course the central Landru computer. On most Trek episodes every room of every building looks about the same; here, there's neighborhoods, at a minimum, suggested to be as diverse as a real town might be.
Heck, for all the times Trek visits a planet with a computer overlord, has it ever
run into one that actually already had an underground resistance? And for that matter, one that is in way over its head as soon as the resistance shows signs of succeeding?
I realize it's easy to say the episode is sloppy or half-realized; perhaps it was. But the result feels to me rather authentic to what a planet would
look like if you had only a few short glimpses at it and then got caught up in an expanding set of crises.
(I admit a certain irrational fondness for this episode as it was my first live-action Trek, but, I don't think it's that