But stories relating to YC companies get a lot more upvotes than stories relating to other companies based on both systemic and natural patterns. This leads to a casual observer believing that YC companies are doing incredibly well and all other companies are not, because you aren't hearing about their success as much. This could not be further from the truth.
The majority of successful startups didn't go to YC just based on sheer volume. I have no doubt YC is a very valuable thing, but I've both seen and participated in groups where a bunch of people who had no idea what they were doing figured it out without YC's help. What current and potential customers think of your company is a heck of a lot more important than what a bunch of YC advisors think of your company.