YC funds a lot of companies who do cool things that aren't very profitable. I don't know what most of them do, and that's great. So many of them serve niches I haven't even heard of. If they break even making someone's life better, then they're a success.
Imagine a world without Stripe or something like it. The current boom in membership services might not have happened. Even VC-juiced Patreon, which I use, handles payments through Stripe. How many successful companies by your measure glue their business together with companies that got their initial funding and guidance from YC?