The same arguments would prove that math isn't a meritocracy. Which it presumably isn't, entirely, but only because nothing is entirely. And if SV is only as much of a meritocracy as math, that's pretty good. Indeed, that's what the word means in ordinary usage.
That's an interesting question, is there an institution or subculture in the world that is more meritocratic than Silicon Valley? If there is, then the author's argument has some merit. If there isn't, then the author is wasting time attacking the one institution that comes the closest to embodying the meritocracy ideal. To what end?
Obviously professional sport. Especially "one-dimensional" sports like running or swimming. The "best" runners in the world are so named because they consistently run the fastest. There are some qualifiers in terms of who has the time and money to train, and access to coaching, but all in all it's highly meritocratic.