[carefulfungi]

I didn't mean to imply there's a single all-encompassing metric or silver bullet, but re-reading, I did kinda write it that way. When you find someone whose code persists a long time, that's often a strong signal of quality contributions. There are of course myriad other ways to contribute critically - ops, culture, finding and fixing hard defects, unusually good understanding of the customer, industry expertise, mentorship, ...