I've worked with a number of clients that have lost senior engineers due to old age or retirement, and the impact is often very significant regardless of how sophisticated their knowledge management infrastructure is. Documentation can not fully replace the insight and situational awareness many of these experts posses and most of the time knowledge management still suffers from the 'not knowing what you don't know' issue. Only well structured 'apprenticeship' programs come close. I know some are going to point to AI, but I've worked in AI for over 2 decades and have extensive experience in Expert Systems and Knowledge Engineering from early in my career. It is not a complete solution. Given today's technology its trivial to replicate 'text book knowledge' but the difficult, expensive problems occur in the margins and its still hard to train AI on open ended / rare occurrences outside of domains that have specific advantages like software engineering. Talented and experienced people are still required. Maybe that will change soon, but AI isn't there yet.