Would you say, at least, that the fact I am not a renowned philosopher is sufficient to conclude, pending further evidence, that I'm incapable of reforming philosophy?

Not given background knowledge. You're on Less Wrong, so there is high probability that you're capable of becoming capable of arbitrary possible things. And capability is transitive, so that means there is high probability that you're capable of that particular thing.

Most people aren't already renowned philosophers, and most of those don't reform philosophy, and for those that did, they usually became renowned in the process of reforming philosophy, so that's not much evidence either way.