The script was a product of the previous writer's strike, and it shows. It needed at least a few more drafts.
On the other hand, a lot of what makes it so . . . difficult for me to sit through without squirming, is all the wretched forced humor. This was a directive handed down from the studio, a result of the positive response to comedy in TVH. There's no question but that the comedy was handled poorly.
And the the budget ran out, the SFX were lousy, and to make matters worse, Shatner was sabotaged on location by other unions who were in sympathy with the writers.
It is what it is, and there's still some mighty fine material in it: the whole sequence with McCoy and Spock recalling their central agonies, for example. Still, while I hate adding new digital imagery to any existing film, I'd be willing to make an exception for this one. I just wish a new script could be added, as well.