Disclaimer: I have not finished Fullmetal Alchemist: Brotherhood, all of this is based on observations so far.
I have a long history with the Fullmetal Alchemist series. I had watched the original Bones adaptation, Fullmetal Alchemist, when I was young. It was a favorite of mine at the time, even though I later learned about issues it has. About halfway through, it stopped adapting the manga's story and built its own, which wasn't necessarily as good. Recently, I picked up the manga, also called Fullmetal Alchemist (although for the sake of avoiding confusion, I'll refer to it as the manga from here on), from my library. The story of it was absolutely amazing, and I understood the reason why so many people frowned upon the anime original story. So, after months of a friend constantly telling me to watch Fullmetal Alchemist: Brotherhood, I finally got to one of the most critically acclaimed anime of all time. I'm nine episodes in, and... honestly, I'm somewhat disappointed. I feel that, at least so far, it's not doing its job as an adaptation very well.