To each their own, but I personally didn't find the book characters flat in any way. They're developed
just enough for my taste.
But my view is that if I wanted to read a character development story, I'd pick up just about any other genre than science fiction. A romance novel, a crime novel, a drama novel, etc. I like my sci-fi when it's about something else than usual, mundane interpersonal drama that real life is so full of already.