I tend to agree - I thought this movie was terrible.
It wasn't the production value or the acting, it was the general theme and overall distaste that the movie left in my mouth after witnessing a poor social commentary on how Humans are terrible.
First of all, if there were alien visitors on this planet, you really think that countries in the world would allow a slum to develop considering how important their presence could be? No. That should be enough to say the movie does not hold water in the sense of important allegory or self-realization.
I'm not going to tell you not to see the movie because I know there are people out there who want to see gore and destruction (which is why there are so many movies about the end of the world). But if you do see it, just realize you're not going to see it for a plot.