Is it more or less meritocratic than teaching? Being an actuary? A politician? A banker? A lawyer? Advertising? Writing?
I don't know all of the answers, but my impression is the market forces on startups (Can you get funding? Can you get customers?) at least pushes them towards being meritocratic. Software also is more binary than fields like writing. The program does have to compile and work.
But is it a pure meritocracy? I doubt it.