These sweeping conclusions are extreme. As a regular listener (and occasional, amateur, performer) of classical music, I find it dismissive and ignorant that the author chooses to paint so many talented musicians with the same brush.
He is instead critizicing that so many talented musicians go unheard because of the name dropping culture of those credentialed enough to be at the top.
Or worded differently, there's no innate talent at the top unless it has been "certified" by insiders.