As far as Amy lacking a sense of purpose, I don't think she was ever really that career-minded. Music was just something that came naturally to her and that she often used as a form of self-therapy, as she herself said. She loved singing and songwriting and had very high standards for her work, and was proud of her work (most of the time), but I don't think she actually viewed it as "work". It was more like, this is her soul in action, which is what made her so compelling. She was about as pure an artist as you can imagine. But when her "soul" got into real trouble, she didn't have a professional drive or work ethic to fall back on, which made her vulnerable.
I think Gaga is incredibly talented, but I don't think we can compare her to Amy in that way - Amy was on another level in terms of vocal ability and her songwriting. When Tony said he's never met a more talented person in his life, he's probably referring to her voice, her piano playing, her ability to write a massive pop hit, her creativity with her set designs, costumes, music videos etc. I wouldn't necessarily say Gaga is more talented than Amy, but she definitely is more of an all-rounder. (side note: I'd prefer someone who is a genius in one area rather than great in many)
What the interview implied about Amy's lack of purpose reflects what Lily Allen said about Amy being such a lost soul. She had all this talent to burn, but wasn't interested in selling a million albums, or worried about falling out of the spotlight, or about having number one singles. I think what she most desired was the approval of her peers and her heros, which she achieved in a couple of albums. Where can you go from there?
This is why i love Amy so much. She didnt feel the need to be number one, she just had such a love for music. It was about just that - music. Not money, not impressing everyone, not to get press. It was just about making beautiful music to Amy. With that in mind, she still received all the attention and success that those who seek attention crave, yet, it is not what she wanted or needed to make her happy, and yet, she only had two albums. Thats how incredible she was. Such an impact on the industry without trying too hard as so many artists do. It was just so natural. She was such a sweet girl too.
As for Gaga being talented in a lot of categories - i totally agree! A restaurant that serves everything is never good at cooking one specialty.