For me, that's what the whole movie was about. The execution of the film could have been better, but I appreciated a movie that took a long, hard look into the abyss. For what it's worth, I thought the ending was purposefully bleak- Cage's reassurances to his kids were supposed to come off as half-assed and illogical, because the truth is they were either saved by random chance or a universal equation so cruel that it decided everyone else on Earth needed to die, and how could you live with that knowledge? Better to dress it up in myth and pull a happy ending out its ass. It seems obvious to me that the movie is largely about how people turn to religion to hide the existential horror of the purely scientific universe, which is either deterministic or chaotic; and while I don't agree with the movie's view, I found it compelling.
If you felt horrified, powerless, and angry at the film's end, I'd say it was testament to the skill with which it was made. While I thought the movie went a bit too far into "Nicholas Cage Crazy Mode," the final scenes struck a deeper chord with me than the usual disaster movies do, and the basic idea behind the film- that life on our planet could be extinguished in an instant, without warning, us unable to do anything about it- is a valid and even important subject for a film to explore.