To my understanding there’s actually multiple ways you can translate katachi / makoto / kotowari (e.g. I’ve also seen kotowari translated as “regret” rather than “reason”) and I think that’s a minutiae of the Japanese language and its implications that I don’t know enough to even really guess at.
Just looking at the narrative, my two cents on what it all means is…
“You still don’t get it do you? That city sucks its surrounding dry, so its residents can live in luxury…Humans are meant to fight parasites.” l requested by @heenata