The peer review system is riven with ego politics. I've submitted a paper before that got rejected by a committee member because I didn't work closely enough with member's research team. He was the one hold out among four other positive peer reviews. The paper ended up getting published in a subsequent conference where the committee members didn't have a stake in my area.

The usefulness of any given idea isn't usually reflected in peer reviewers' opinions, but whether it actually is a good idea, and sometimes that happens outside the peer review system. For example, I don't think even Larry and Sergei's PageRank algorithm was published in a peer-reviewed conference, and we all know what happened there.

Novelty, on the other hand, is probably a lot harder but even those ideas fall through the ego-drilled cracks of peer review.