mentorship matters, and what you tell and how you treat people who are coming up matters.
https://twitter.com/MathPrinceps/status/1131980522450587649 …
Indeed, it matters tremendously -- which is why teaching the practice of mentoring itself is so crucially important. But when most advanced education takes the form of broadcasting (i.e., lectures), mentoring (which is relatively expensive and inefficient) gradually decays.