What message did you get from this movie?
I'm not sure if this is what the makers intended, but the message I got from Beasts of No Nation is that Africa will never ever attain modern standards of civilization.
They are still the same savage warrior tribes they were in the distant past, only with AK 47s instead of spears. They had a chance to advance through colonization, but they kicked out the Europeans and rejected everything about European civilization except the weapons.
In another hundred years they will probably still be dancing and chanting and mutilating their enemies with child soldiers as they slaughter each other using energy weapons and powered armor.