It is more likely that the interview process is broken and missing the right candidates, than it is that the interviewees are all mediocre. Most interviews are very non-inclusive the same way that the main track of school is becoming less and less inclusive. Different people need different methods to bring out the best in them.
Here's a thought experiment for you: if the interview process is so broken, why hasn't some tech company succeeded and become famous for an improved interview process, e.g. "Moneyball style"? My guess is because the process is not actually that broken, at least from the employer's perspective. I'm sure the interview process could be changed to be less regimented and more "inclusive", but that's also likely to reduce it's predictive power (i.e. you're more likely to make bad hires, and from a company's perspective that's almost always worse than missing out on a great hire).
Hiring is guessing. Firing is knowing. If the hiring process worked, we wouldn't have layoffs like we do.
Sure, an argument exists around "you shouldn't've hired that many people", but that is different from an argument of "the hiring process can't discern good hires". The former is a management & long-term planning issue, the latter is how interviews are conducted.