The Confusing Case of Edgar Wright's World's End

For this first of many blogs to come I'll analyze a new movie out in theaters right now called World's End, a tale of 5 friends who set out to tackle an old high school mission of theirs, to hit 5 bars in one night. Of course the movie isn't really about the drinking capabilities of the film's main character Gary King, rather it focuses on Gary's underlying issues and what drives him to make his (mostly terrible) decisions. What's confusing about this movie is ultimately what the theme of the film is, what it all means.
[WARNING SPOILERS] Gary King is an absolute jerk to his friends, he is an all-around unlikeable person and to be frank by the end of the movie he actually causes the apocalypse. He's the sort of person who acts like nothing has changed since high school, that all the old rules still apply and he can be a kid at heart still, even referring to himself by as he did as teen (The King and also, "The once and future king.") Of course his life isn't quite so royal, in the beginning  of the movie he's introduced while sitting in a rehab meeting, his friends even allude to some sort of substance abuse. The story sees Gary drinking a serious amount of booze, but ends with him ordering a very symbolic glass of water at the bar thus 'getting clean.' On top of his success with tackling his addictions, Gary also gets all his friends back... at least to some extent. To clear that up, Gary gets back the younger and cloned version of his friends. The real ones had begun to hate him at that point, but Gary gets new friends who roam with him through the post-apocalyptic world. This then begs the question does Gary 'win?' Is the theme of the story really that 'if you hold onto the past hard enough you might get it back'. Maybe I'm missing something but out of all the characters Gary is the least deserving of such a happy ending. It could also be possible that the theme could be 'some people deserve a second chance at happiness.' But these seem wrong, the tone of the film is dark and somewhat cynical, so maybe the director meant to deliver that the theme is 'the one who doesn't deserve to win sometimes does.' Overall, I was left pondering over what the movie was really trying to tell me.
What I'm trying to say at least is that the theme is hard to derive from the film, director Edgar Wright throws the audience for plenty of loops. Even after reading several reviews and analysis I find it difficult to put into words exactly what the purpose of the story might have been. The ending didn't seem to be fair at all, the characters who appeared to deserve something were left with nothing, but Gary gets back everything he one lost, and he gets it for no apparent reason. I'll have to watch it again and see if I can derive anything new from it.