Migi was the one often advocating they flee. He was always about his own survival. After his mother was killed, Shinji wanted nothing more than to kill every one of them. Until the final Tamura Reiko arc, he was out for blood and didn't outwardly feel anything but hatred. That arc was full of your "missing" philosophical aspects.

That's why I thought she was the most interesting character. She was still filled with the compulsion to eat humans, but she was deeply concerned with why. In the end, she even started to care for the tiny life she had brought into the world, protecting it while letting her own body take the abuse. A lot of it was underneath, but her arc definitely had the most thought provoking questions from their point of view.