The problem is, virtually no VC is taking cold calls anymore (did they ever, really?). YC is great if you are early stage and need the money, networking and yes, validation. Their knowledge and experience are also very useful, but they already make it available to the public for free (which is amazing in itself).

If you can bootstrap a business without needing any of the above, that's really great and you should do it. But that depends greatly on the type of your business.