I'd say it was good by accident. Amethyst struggled with self-worth, like half the cast, but it was actually justified in that Rose had caused it. Unfortunately, that was given away in only one bit of dialogue though. Outside of that, Amethyst suffered from shitty writers over-compensating; because they didn't know how to write legit character flaws. So, she was mopey and a shitty person to be around, whenever the focus was on her. Yet, whenever the focus wasn't, she went back to being a fun character.