Princess Kaygua was one of those movies in the likes of Synedoche, New York and Tree of Life because they all make a broad statement about life itself. In doing this, those films tackle heavy themes such as death, love, and happiness. Just making an ambitious film like this would receive praise alone due to the stigma placed on animated films being "childish" however, not only does Takahata do a fine job tackling these themes (fantastic with love) but his commentary on desire and greed are especially biting, going above and beyond the precedent placed on animated films.
In a way, its fair to call Princess Kaygua a cynical film. I only have seen four other Ghibili films and all of them have a layer of optimism within them even in the worst of situations. On the other hand, the princess spent most of her life being unable to connect with the world (due to discrimination between economic class and even animals), live a life of freedom, and happiness. All goals she wanted to accomplish on Earth. They do end up happening but only right before Kaygua dies, in between was the crushing weight of mediocrity formed from greed and rules rooted from the lust of the higher ups in society (a critique of patriarchy.)
This greed motivated the father in the fist place. Through the film he made "opportunities" for his daughter so he can indulge in luxury. The puberty party made transparent the verity of his motivations because he put Kayguya on display as a trophy while throwing a party, excluding her presence as if she is just an excuse to socialize with rich people. Takahta made a bold statement with her father, that greed is a primary motivator for people since people like him would not go to reach such great heights had there been nothing to gain for themselves. Even the princess blew their wealth away just to have Kaygua as a trophy, with that their superiority is lost. Its funny how none of them ever seemed contempt with there life, a life empty of love.