Kirk's really an @$$ in the film, what he does to Decker is simply unforgivable. I suppose Roddenberry might insist things are different in his 'utopian' 23rd century, but there's really no real-world precedent for assuming your career would bounce back after someone's yanked away your promotion -even temporarily- during a time of crises. You're pretty much finished.
I think what it really boils down to is Roddenberry didn't know his own characters as well as the writers who wrote for him did, and the latter largely thanks to receiving input over time from the actors themselves. I believe this was true with both TOS and TNG. The shuttlepodcasters on TrekMovie, in their review of Nemesis, commented that under Stuart Baird's direction the TNG characters seemed to have reverted back to their Season 1 status of development. I think the same is true with TMP under Gene Roddenberry and Bob Wise, in that it's almost like most of the TV series never happened and we're picking up with Kirk and Spock shortly after 'WNMHGB' or 'The Corbomite Maneuver' in terms of where character development (let alone character chemistry) seems to be. I believe it mostly 'works' given the movie's premise of almost everyone having been away for several years, however the experience still left Nimoy not really wanting to return to ST afterward (yet again) and that right there (along with the less than enthusiastic reactions of critics at the time) tells you something was way off. You can't help thinking Dorothy Fontana or David Gerald could have pulled a better script out of the same story. And... Kirk really does come off as an @$$.
