I have a theory about teen friendly fiction and movies, and it all has to do with what children want. Preteens want to be teenagers, because, you know, teenagers are cool. Teenagers want to be adults, with all the benefits of being adults, like romance and being able to make decisions, without all the responsibility that makes being an adult such a drag.
So it is not surprising that a teen friendly movie like The 5th Wave would kill off most of the adult characters leaving the adolescents in charge. The main character, Cassie, practically acts as a mother to her younger brother Sam.
As far as alien invasion movies go, the movie is not bad, but it is also not great. There are echoes of plots and characters from other teen-centric movies that seem familiar. It is only slightly better than a good science fiction TV show, but that quality also makes it a good rental.
The 5th Wave has only a 17% rating on Rotten Tomatoes, but I see nothing major wrong with it. I enjoyed the movie.
The movie is a setup for a sequel. Given the generally negative reviews, I am not sure if we will get a sequel or not.