On a related note - I helped review a little over 100+ YC applications since getting in myself in S20 as a way to give back. There were a lot of bad applications or just ideas that seemed over saturated (a social media for some niche as an example). Literally tens of thousands of people apply for YC every batch. I personally recommended around 20 with around 15 getting interviews and around 10 getting in. I only recommend companies that I personally would want to invest in if I had the capital. YC has funded a handful of competitors in my space (PaaS) and I actually had calls with them to exchange notes and see where we could help each other.