>The main thing missing from this IMO is an element of chance or randomness, the ability to incorporate “unknown unknowns” into your life.

100% this. When I started working in recruitment, it was literally intended to be a temporary means to an end. I stumbled across Hacker News back in 2010 and accidentally uncovered a niche (tech startups) that has resulted in a career where over the past 15 years has evolved into holding VP level roles at YC startups to now running my own successful recruitment and HR advisory business for startups. I can legitimately attribute that entire path and growth to accidentally stumbling across this website and couldn't possibly have guessed the impact it would ultimately have on my career.