It's not an exciting score, but it works brilliantly with the movie. This movie didn't need an exciting score, it needed one that blended with the raw, naturalism of the film, and that's what it did.
It is definitely simple, but people confuse simple and basic with bad. I've heard a lot of scores that people won't shut up about that aren't all that great at all (A lot of Zimmer's work).
I wouldn't have wanted any alterations to it, and it variates to each situation that makes it not get to repetitive. Albeit, it's not necessarily a score you're going to just sit and listen to, but it enhances the experience and without it you'd lose a lot of that naturalistic immersion.
It's very atmospheric. Add to the fact that there weren't a lot of great scores this year, it kind of automatically is in the top 5-7.