"FANGS hire plenty of senior talent" Following this logic the median/mean age would not be 29. But we know it is - since that number is from lawsuits which did their due diligence with court ordered discovery. The other way to follow this logic is that age and experience is not correlated. EG. A 23 year old developer could be senior. Maybe this is the case?
There's a fat pipe of people in the E3-E5 range, but it starts to drop at E6 and even more so at E7, and E8/E9 are unicorns. The median is going to be in the E3-E4 range as there is a tremendous amount of churn there for performance reasons.
This is why the question of "what is a senior engineer?" is so important. FANGs are thirsty for E6+ and they hire plenty of them, but there are not enough of them in the world as it's hard to become one without credentials from another FANG.
Part of the reason for this is that there are not many big tech companies that marshal similar forces. For instance, a E6 may be responsible for designing a $50,000,000 system which is definitely a rare skill.
Unfortunately, the senior title is basically useless across the industry. Does it mean time spent doing stuff? Well, time spent doing what? With what kind of budget? What kind of responsibility? What kind of operational burden?
The cruelty of reality is Price's Law comes in for a double whammy. First, for humanity, there are only so many big tech endeavors that investors/customers support so the scope is limited in the number of companies that have big challenges. Second, within a company, there are only so many big-tech problems.
The hardest part of my job was creating scope that was relevant for the business, and I left as an E8 where my great pride was helping two people achieve E7 and a swath of people achieve E6. I was not creative enough to create the scope for another E8.
I tried, failed, and bounced to create room for someone else.
