Miyazaki is anti-war, but he's also extremely pro-ecology as is obvious in most of his films (Nausicaa is an obvious one, but perhaps more obvious would be Pom Poko or Totoro). Broadly speaking, he advocates balance in all its forms. A lot of his main protagonists are strong female characters, and not the "overly girly unicorn princess with magical powers" kind. Violence, like greed, is a disease as opposed to an end (in fact those two concepts are often expressed together in his films, e.g. Spirited Away).
But maybe the best accomplishment in most, if not all, of Miyazaki's work, is his ability to capture the interest and the imagination of the viewers without resorting to cheesy gimmicks, gratuitous violence or sexual innuendos, which seem to be the go-to for a lot of cinema (animation and otherwise, Western and Eastern).