tl;dr silicon valley isn't the liberal utopia and therefore not a meritocracy.
There are two separate problems here: What opportunities you have, and what you do with the opportunities you have. The latter is where merit comes in. The former is where the -isms live. Those who are fighting disadvantages must spend tremendous amounts of personal energy just getting to be on the level, merit-based ground.
Now, I think the author is fundamentally wrong in a lot of ways. She's faulting Silicon Valley itself, but I think the problems are upstream, and she did basically no analysis on that. So white males are getting the majority of venture deals? What's the ratio of deals applied to deals received? White males are the ones looking for venture deals and other Silicon Valley entrepreneurial stuff. No one is stopping women, minorities, etc from doing the same thing, and I doubt there's a significant punishment for them compared to the other 99+% of companies that get rejected.
And another thing she glossed over is the meritocracy of simply getting to that point. You don't get to waltz in and get showered with angel money just because you're white and male. You have to deliver. Those institutional biases to twenty-something Stanford CS dropouts reflect both the kind of people likely to succeed, and the kind of people likely to choose the path at all.
So while the article itself is mostly a fail, there's some truth to it. Whining about how liberals hate merit, on the other hand, is just political nonsense.
It would appear that Marx rejected the Labor Theory of Value. So do I, for that matter. It does not account for the quality of labor, scarcity, or demand. Labor is a factor in value, but it's not the only factor, or even the primary one in many cases.
Leaving behind the 19th century anarchists who were still wrapping their heads around an economy that didn't even exist yet, modern practitioners of the labor theory of value are classic examples of theorists in denial of reality. If the theory and reality are at odds, then clearly reality must be wrong, correct? But they're also pretty irrelevant outside their little ivory towers. Power is collected by realists.
Personally, I think it's much more interesting to consider where capitalism fails at measuring value - basically, the idea that all value can be measured in terms of fungible currency, and anything that cannot be measured in currency therefore has no value. This problem sticks out like a sore thumb at awareness of externalized costs (or the lack of awareness, in the case of the hordes of neoliberal "conservative" fools who have no idea what a real free market looks like). But so much of value can't be measured in dollars.