The story was a good one, I grant you that. But I do not agree that it was well-executed.
For what it was -- a modestly budgeted 1964 television production by a studio with absolutely no prior experience making science fiction -- it was
astonishingly well-executed. It came close to the look of some feature films of the period.
And again, if we define "success" and "failure" in terms of whether it achieved what it set out to do, then it was very much a success where its execution was concerned, because it convinced NBC that Desilu was capable of producing a science fiction TV series on a weekly basis.
You are probably better read than I on Trek history so correct me if I am wrong here but wasn't it incredibly unusual for a pilot to get a second chance? Doesn't everyone always talk about how incredibly lucky GR was that they asked for a second pilot (and wasn't that the doing of a minority of execs--1 or 2-- who argued to give GR that second chance) and that the trade off for GR was that his budget would get cut down incredibly?
No, I've already explained this. Yes, second pilots were almost (or completely?) unprecedented, but the reason for it in this case is that "The Cage" didn't fulfill the purpose of a pilot, which was to represent what the budget and logistics of a
typical episode would be. It was a pull-out-all-the-stops production to show what the studio was capable of achieving, and thus it didn't give the network a good sense of how much a routine episode of the series would cost them -- information they'd need to have in order to decide whether they could afford to buy the show. So they needed to ask for another pilot that would represent a more typical production. In a sense, "The Cage" was made to sell Desilu itself, and "Where No Man..." was made to sell
Star Trek.
So it wasn't "luck" that GR got a second pilot. There was a clear and practical reason for it. And the budget wasn't "cut down incredibly," it was just set to represent a typical episode rather than the lavish, all-out production that "The Cage" was.
We don't know the details, but that seems to be close to the truth; he declined to attend a screening of the pilot, instead sending his wife, who told the producers that he was "a movie star" and wasn't interested in television. (It's not like he was asking Desilu or the Norway Corporation for a movie deal -- how could they possibly get him that, and for what?)
As for his performance, he wasn't as engaging a lead as Shatner turned out to be, but I'm not familiar enough with his larger body of work to know whether his performance style in "The Cage" was typical or unusual. And it would be presumptuous to make guesses about what motivated him in his performance choices. I don't recall any accounts claiming that Hunter was in any way unprofessional in his work on "The Cage."
It has nothing to do with "PC" -- a label that should never be used because it's just a lazy way to attack and dismiss an opposing point of view rather than engaging with it fairly. I've explained what I meant by the phrase. "The Cage"
did succeed in convincing NBC that Desilu was capable of producing
Star Trek, and that it was worth NBC's while to pay for a second pilot. But it wasn't enough in itself to sell the show; it was the one-two punch of both pilots combined that closed the deal, the first to sell the studio, the second to sell the series. Hence a partial success. Consider it the first round of an ultimately successful negotiation.
No, that's the opposite of a fact. "The Cage" almost
sold TOS, but wasn't enough to do so on its own, because it didn't represent a typical episode -- and, yes, because it needed a stronger cast. It makes no sense to say it "almost killed" something that wasn't even "alive" yet. That's getting it backward. You're talking as though it was entitled to exist and "The Cage" almost prevented that from happening. And that's just nonsense. There was no entitlement. Roddenberry had to prove that his show had a right to exist. And "The Cage" proved to NBC that
Star Trek was worth pursuing
if some adjustments were made. It convinced them to pay for a second pilot, something that had almost never been done before. How can that not be considered a remarkable accomplishment? If it's a failed pilot, it's surely the most successful failed pilot in the history of television.
I remember seeing an interview where GR actually admitted that the money he was given to make The Cage got to his head and he admitted that the pilot was not at all what he had promised the studios.
I don't remember that, but many of Roddenberry's accounts of the past were notoriously unreliable. Even if it does represent a facet of the truth, though, it certainly doesn't prove that the pilot was a complete failure. It merely affirms what I've already acknowledged, that the network felt the pilot needed work. But they were still sufficiently convinced to take a second chance, so it succeeded to that extent.
What if he could have appeared as a guest star playing some relative of Spock's (instead of Luckinbill who was terrible in TUC).
Maybe that's because he wasn't
in TUC.

And I thought he was one of the few good things about the movie he actually was in,
The Final Frontier.