Well, I actually used to feel almost exactly the same about this one, too. It was another of those episodes I liked to forget about, but after rewatching it, I think the acting in it is very strong and the actors really put a lot of effort into it. I absolutely love Alexander's character and his interaction with Kirk. Michael Dunn was great, I love his performance. I love this part especially:
ALEXANDER: Anything you want, Just ask me. Anything.
KIRK: Thank you, Alexander.
ALEXANDER: Think nothing of it. You saved my life. I think I should tell you that
KIRK: Tell me what?
ALEXANDER: Well, just that I never knew any people like you existed.
KIRK: Where is everyone?
ALEXANDER: They're all in chambers, meditating.
KIRK: Alexander, are there other Platonians like you?
ALEXANDER: What do you mean, like me?
KIRK: Who don't have the psychokinetic ability.
ALEXANDER: I thought you were talking about my size, because they make fun of me for my size. But, to answer your question, I'm the only one without it. I was brought here as the court buffoon. That's why I'm everybody's slave and I have to be ten places at once, and I never do anything right.
SPOCK: How does one obtain the power?
ALEXANDER: As far as I know it just comes to you sometime after you're born. They say I'm a throwback, and I am, and so are you. I'm sorry. I shouldn't have said that.
KIRK: Don't worry about it. We're happy without it.
ALEXANDER: You know, I believe you are. Listen, where you come from, are there a lot of people without the power and my size?
KIRK: Alexander, where I come from, size, shape, or color makes no difference, and nobody has the power.
I bolded that last part, because it's nice to think the future will have that. We don't have it now 50 years later but I'm still hoping for the future.
And about Parmen, he is very cruel and sadistic, any conscience or reservations about doing something other than his whim is gone from him because of the long years of having absolute power. While he doesn't have the strength Mitchell did, this is what Gary was turning into. So how do you portray this? Have a character spout it out? Or do you show it by having Parmen abuse Kirk and Spock? Of course it's unpleasant to see! That's the point, isn't it? If it was just ok or painless, it really wouldn't show how cruel he is. And how is flying through a barrier and absorbing energy that gives you powers more complicated or thought out than absorbing a local element that gives you powers?
And then once the use their reason to determine the source of the power, and are able to administer that to themselves, Kirk takes the power and kills them all and sets himself up as the new god, right? Oh, wait no he actually doesn't harm any of them and just negotiates from a position of strength, which
is classic James T. Kirk. He has always been exactly that, he talks with his enemies and makes them, if not friends, at least no longer enemies anymore, if possible. Some enemies do not want to stop being so, then and only then does he resort to anything more permanent. This stupid mischaracterization that Kirk shoots first and doesn't negotiate with anyone is just blatantly wrong and divorced from what was shown.
So having the power, he spares them and takes Alexander and leaves. Like he spared the Gorn, wanted to take the first Romulan Commander and his survivors to safety, offered the second Romulan Commander guest quarters, opened communications with the Horta, he and Kang defeated the * together, offered the Kelvins the planet they crashed on to live, and I could go on, there are many more.
Sorry if I seem like I'm picking on you
Grant, that is not my intention at all. That last part especially was not directed at any one person but at the people that perpetuate that stereotype that all Kirk did was zoom around killing and screwing. It's stupid and the show would have never been remembered if it were true.