I think it goes to show how impossible it is to judge an idea. YC itself doesn't pretend to do this with the ~15,000 applications they go through each cohort. They try instead to look at the team, look at their progress, imagine what would need to happen for the company to succeed at the level required for them to get the returns they seek.

Founders should have a thick skin when it comes to criticism on HN, because we don't know either.