> Investing in relationships has been the key job security hack for me

Connections frequently take precedence over skill! It's hard to determine skill through a piece of paper and some coding exercises under pressure. But a connection give a good signal on that and truth is almost no job requires maximizing skills (exception is at the bleeding edge and even there not always). It's also a signal about soft skills, trusting the connection isn't going to suggest someone that's difficult to work with.

I think it's easy to miss because we're often so data focused and because we want meritocracy. But the truth is you can't measure everything and not everything that's measurable is easy to measure. It takes more work to determine if some junior from a no name school is better than someone from a prestigious school. By connections make that easier to determine just like the prestige of the school serves as a signal, even if noisy. I think it's important to remember how this compounds too. Like your first year undergrad at Stanford is probably at a very similar experience level to a first year at a community college. But that gap widens and the gap isn't only due to coursework and lecturers.