Kirk is a starship captain for reasons both in and out of universe.
It's Star Trek, sans :TNG, DS9, VOY, ENT. It requires Captain (not Commander, Lieutenant, Ensign or Chief Petty Officer) Kirk to be in the chair. It was always going to be thus.
In-story: Blame Pike and Nero. Nero wiped out a bunch of ships (and a considerable number of officers) and Pike was in such a hurry to inject the "look before you leap" element he got Kirk in the chair. Too soon, as it turned out. I get that the reversal was lightning quick in the sequel, but imperfect execution does not mean it was not addressed. Part of that quick reversal, though, reflects Marcus' belief that Kirk could be easily manipulated--a more experienced captain might well have taken the time to examine things a bit more fully BEFORE taking off from Earth. So Kirk is twice put in the chair by people who value the fact that he's not like everyone (anyone?) else in Starfleet--one naively and one nefariously. It's not Kirk's fault they keep giving him the chair.
My sense is that a lot of the complaints made about the way Kirk "gets the chair" are the result of the compressed nature of film vs. TV series storytelling. This is not to say the films are perfect and people are too stubborn to accept it (I quite like them, but they're not in my top 100 films of all time or anything). And not all the criticisms of the film can be explained by this reasoning. However, I do think a substantial amount of criticism is levelled at certain story elements being necessarily compressed (which is a separate point than done well).
I find it refreshing that the characters are not yet as cohesive a unit as in TOS. They are, after all, a decade or so younger and less experienced. But that's me.