"And like the Goulet TV version, why cast a great ballet dancer as Harry Beaton and then barely allow him to dance?"
I think part of the answer to that is the answer to what is the cause of several of the film's flaws: Gene Kelly's ego. And one other important factor: I believe Vincente Minnelli was going directly from one movie to another at that time, and he seemed to have his heart in few if any of them and was perhaps not able to focus on each one while working on it.
"Oh, I just remembered one other specific thing I disliked: Jane is so unpleasant (and she is also is on the recent recording). Really, she shouldn't be. They're just not right for each other, but if you really just look at her lines, she's very reasonable and patient with him, and he even seems to recognize that. I think it's wrong to make her a snotty bitch. We really don't need to have the deck stacked so totally against her in that way."