One of the other things that bugged me about the movie was the way that Miyazaki cut out the revelation that Sophie's mother and sisters actually did care for her.

Yes; because it goes toward Sophie's realization that story-traditions don't rule her life after all, that she's not doomed to failure as the eldest of three sisters, that she doesn't have to be whatever is expected of her, that her stepmother is not wicked, and her sisters are also iconoclastic and rather awesome people.