I don't normally throw TOS episodes under the bus, but when I do... it's this one.
Hand on my heart, I think both "The Alternative Factor" and "Spock's Brain" are better episodes.
To really compete, we have to sink to the likes of "Plato's Stepchildren," "The Lights of Zetar," and "And the Children Shall Lead."
Yes, my opinion has changed over time. After seeing the similarities to
Turnabout (1940), I find it really hard to excuse this phoned-in pile of tripe, especially with all of the other issues. At least with all of the other episodes under discussion, including TATV (a.k.a. The Thing

)
some effort was being made to do something original (AFAIK), not just take a preexisting idea, file off the serial numbers, mix it up with low effort, and pass it off. WTF is security even doing in the episode? Their mission is to protect the starship, not follow the captain off a cliff.
Anyway, I digress. I was just trying to interject a sort of, "Well, it could be worse," form of consolation, given that other series' finales were already under discussion. But, yeah, mileage varies, and that's OK.