why dumpster diving? and those guys cannot be replaced by any number of junior devs - that is exactly the problem with them retiring. they know the legacy stuff nobody wants to touch but everything depends on.
so, from that angle this writing reflects very poorly on the author and his work experience.
having said that - the title could fit just about any lawyer. law is the crappiest codebase that you have to spend a lifetime learning. especially the german tax law - but it guarantees a very comfortable income.
also in defense of people like that man i'd even argue that mastering a legacy codebase is mentally and motivationally not that different form mastering a game like chess.