First of all, let me get this straight: the plot is very repetitive. There are a lot of robot battle scenes that aren't particularly exciting. The plot is woven around the individual pilots, to the point where they seem like individual independent short stories that have been tied together.
What's the point of reading this then? Well if you're looking for a simple thrill this manga is not for you. The manga really shines in its dialogue, its exploration of the humanity behind each of the characters. I was surprised that such an existential manga existed. Of course, the manga leaves you empty and kind of hollow, and there is no resolution; but this is so with any existential work.
I was very impressed by the author's treatment of existential dialogue. Spoiler: Upon learning the true nature of the "game", that is, every pilot is to die, each pilot deals with this crisis differently. The most important parts of this manga has to do with the fundamental points of existentialism: why them? Why not anyone else? Kirie mentions that in a movie, anyone's death is equal to the death of the hero - and that is the idea that the existence precedes essence; just essence of the "hero", created through the construct of the movie, is no better than an extra in the same movie. It is a biased viewpoint. The extra has probably validated his existence through his choices and his behavior.. just because the movie dictates that these are the ones to root for, which is their "essence", does not mean that their death is more tragic than the others.
This dialogue is especially brilliant, because it pertains directly to the heroes of this manga.
Other existential themes involve the absurdity of life. We learn that SPOILER every earth is going through the same thing, and Kokopelli did the same thing for his earth as well... it is an endless cycle. The way that the manga ends is perfect, with the dungbeetle sitting, starting a new cycle, over and over again. The world is neutral, it is not biased. It goes on, no matter the thoughts and the beliefs of the people. They ask who it was that made this game, and dungbeetle can only claim that it's always been like this... and so it is with the futility of life.
And of course, like any good existential work, it is all about death. In a cyclical world that seems without purpose, everyone in the manga still cherish life, as this life is given meaning by the finality of death.