"[...] at the very least, would have learned from the knowledge passed on and inherited from them..."
Many people who consider themselves "developers" appear to have a mindset that precludes them learning from other people's prior work. They always want to develop from the ground up based on their own ideas - rather than build on, or tweak, something that does most of the job already.
In my support career there were several times when I had to rip out someone's large "blister" patch that created new problems by fixing symptoms rather than the root cause. I would then take the time to identify the root cause - and often it merely needed a small code tweak to fix it elegantly and permanently.