I haven't watched it for a while (I did pick up the Blu Ray but I was waiting until I could sit down and watch them back to back) so some of my memories could be wrong but for whatever it's worth.......
I would agree with some of those notes (insofar as I think and expect watching them back to back would make them feel like two parts of the one story by the end of which you've sort of had the 'foundation course' in what the prime elements are of the Trek Universe and also the new timeline versions of those elements.................fair enough we could argue that maybe didn't require two films but with Trek you sometimes have to take what you're given over what you wanted!) but I liked that there's an element of pliability in the character of Marcus. And the others.
Because they used the events of the first film as a generator of the storyline of the sequel then you can have the discussion of was Marcus right or wrong to make his choice? He looked at the environment around him post Vulcan and made what he admitted was a 'tactical risk' when he sought out Khan, and enemy and began to use him for his own ends.
(though in fairness I think Wil Wheaton puts it slightly better saying the same thing in his review of the film)
You can in fact have a conversation about what he chose to do employing both points of view so I don't personally think the film took things too simply on that front (this debate has happened over a multitude of real life events and responses. I don't believe that's necessarily ambivalence but more an attempt at a grown up stance whereby life makes people disagree over what to do and both arguments can have validity). It could be considered a dramatic trope but sometimes the old questions are still the ones that make people talk most.
Similarly, I think Kirk giving in when confronted with the man who killed Pike shows that he's still struggling with the decision he has to make at this point. He's already being played by Marcus (though obviously we don't know that at the time) to murder the man extra-judicially and he's being scrutinised by Spock to do the opposite thing and allow the rule of law to make him accountable for his actions, and I think without that struggle being demonstrated (and briefly given into) what you would have is a less compelling character moment of internal conflict and instead have a character on a soapbox. Similarly I think Spock then finds out taking the moral high stance isn't always easy when the situation turns around on you and he loses (or thinks he's lost) Kirk. Which again, I think, mirrors real life more than it doesn't.
'If the Apocalypse starts, beep me!' - Buffy Summers
'The sky's the limit.....' Jean-Luc Picard, 'All Good Things'
courtesy of Saquist