In 1995, Ellison published the original version of this teleplay. I remember seeing it in a mall bookstore, with a photo of Harlan posing with Shatner and Nimoy (both in costume) on the cover. The introduction was vintage, ranting, profane Ellison.
I glanced through it and noticed some of the changes, but given that it was a prime-time series, I totally understand why portions were rewritten. It's probably the most highly-acclaimed episode of the entire Star Trek franchise, yet Ellison has been bitter about it for decades. Stereotypical artist - so gifted, but "not quite normal".
I have that book and have read it. I agree that for the most part the changes were justified.
If you look at the Wikipedia article on “The City on the Edge of Forever” you will find summaries of the original treatments.
You think he was bitter about that, ask him about what the writers did with "A Boy & His Dog!" Or ask him what he used to think about "She Hulk" in comics (yes, it's been a very long time since I've seen him or spoken to him in person).
Mark