Here again, I think the complaint is the opposite. He's saying that if you have traction already, you don't need YC. You're further along than what they offer. They are there to help people who have no traction and no metrics and no money.
The sad thing is that the hype cycle is more important than the product delivery. Many huge investments are made on products that have nothing delivered. It's more BS than we'd like to admit. My own product failed in the market because I focused on the MVP and making it real and not on getting hype out and using that to get money.
'Traction' is a pretty wide spectrum. Having some early traction with a small number of users who love your product is a sweet spot for YC imho, especially if you don't have connections or a 'pedigree' in the startup world. At that stage, VCs typically aren't interested unless you have something else going for you. YC helps you take the few sparks you've got smoldering in some twigs and turn it into a little fire that is potentially interesting to angel and seed investors without too much embellishment.
The sad thing is that the hype cycle is more important than the product delivery. Many huge investments are made on products that have nothing delivered. It's more BS than we'd like to admit. My own product failed in the market because I focused on the MVP and making it real and not on getting hype out and using that to get money.