"can" I think is true for some large majority of people. It's just that most people get discouraged well before the point at which they've devoted enough of their lives to their endeavor to be truly excellent. So in that sense, maybe they "can't", but it is not due to an innate talent deficit, but a psychological deficit (which I believe can also usually be addressed with enough attention and intention).

I don't entirely agree.

In this context, excellence is a stand in for what Aristotle calls arete in the Nicomachean Ethics. Or if it isn't, it should be; this conversation spans millennia.

For any given field of endeavour, we may aspire to excellence, but it isn't given to all of us to achieve it.

However I must believe that arete is, if not available to absolutely everyone, at least, an accessible part of the human condition, to the point where someone who was born with such a paucity of gifts as to make this impossible, I would consider disabled.

Schizophrenia comes to mind as an example of a condition which makes this very difficult. But Terry Davis shows us that it isn't impossible.