This movie has a great many ideas that could have been put together effectively, had the director and writers had the right goal in mind. The goal that they chose was to make a film of self-discovery, early teenage romance, and a coming-of-age story set in the midst of apocalyptic desolation. All that would have been fine except that too many necessary parts of the puzzle were not available.
As always, I am here to brazenly presume that I could do better! If you're interested, I have some "fixes" I would have applied had I been involved.
1. The biggest missing piece, of course, is the acting. Coming-of-age stories are typically dramatic in the extreme, and very demanding of the actors involved. Early love, infatuation, disappointment and broken hearts, betrayal, jealousy, depression, passion, the death of loved ones.. It should have been evident from the start that all of the young people involved in this film don't have the acting chops yet to pull this off. I would instead suggest that the film be focused much more on action. Less time playing sad music and watching downcast eyes. I got REALLY tired of watching the hero periodically give up and slump to the ground in defeat, especially since he didn't seem to be trying very hard. Don't ask him to portray such feelings, instead keep him in the fray. Bring on the monsters!
2. Budget concerns. Obviously this is not a high budget feature. That's OK, they did great with what they had. I think it could have come off a little bit better if they'd put more emphasis on dirt. Quite frankly, all of the important parts of the movie were much too clean to be convincing. The actors looked freshly washed. Some of them even have hair that can't exactly keep it's look if you live in a garbage dump. I would suggest filming after they'd actually lived in the dust and sand for a few days without a shower.
3. Direction and Pacing. The story kept slowing down, the motives of the characters appeared to change constantly. Just have a goal and stick with it. The entire story appears to happen within a day! That's not enough time for the characters to grow and reach the sort of conclusions they reached. I felt as though this should have been at least a few weeks worth. Some re-writing is absolutely essential here. Character growth takes time. If you really want your story's timeline to happen quickly, leave out the drama and take my earlier suggestion to bring on the action.
4. Violence. This is conceptually a very violent movie! This movie has monsters, sword fighting, killing, it's all here. And yet blood was mysteriously absent. The fighting stunts are weak and difficult to follow, and completely nonsensical. Blood is a must, and death scenes should be on camera, not suddenly off camera and assumed.
5. Common sense. This is tough and maybe even unfair, but too many things happen that simply don't exemplify the sort of things rational people would do. The writer should have sat back, had some random people read the script and ask what impressions came to mind. People would immediately give some corrections. It can be hard for a writer to pull his head out of his work and look at it objectively, so outside input is critical.
6. Casting. There was really not much need to have so many actors in this film. Or rather, there was no need to have so many extras. Too many of the kids said and did nothing, all the way until they were removed from the story. Why not just trim the cast down to the more important characters?
I'm not certain who the audience for this movie was supposed to be. Is it a family film? It has some pretty violent undertones for a family film. It's clearly a sci-fi monster film. It has all the elements of something I wouldn't want my children to watch, and yet it pulls it's punches, coming off as surgically clean. It's like a horror film with no horror.