A bunch of people do a lot of stupid shit. They all die.
Yes there's some attempts at some philosophy here and some of it works (funny enough, all of the "quiet" scenes work best) but most of it is just not all that new and not all that interesting.
All of the tacked on action stuff at the end was pretty bland, superfluous and almost like an obligation. I did quite enjoy the action in the middle when the "sickness" first starts however.
Not a direction or casting problem - and the movie looks great! - but rather a screenplay problem in my opinion.