You're right. Who knows what agents are looking for. I've actually been fortunate enough to have two (of 21) rejections come in the form of personalized notes. Both said essentially the same thing "...beautifully written, but can't find sufficient passion to represent you..." Neither would offer anything more. It's my first novel. I feel lucky to have gotten responses with my name on them - most are, well you know. But if it's beautifully written, why can't they find passion? I have passion.