I've yet to meet someone who can keep the entire complex, humongous system in their head (we're talking about a system that have been developed for 5-7 years wi

I've yet to meet someone who can keep the entire complex, humongous system in their head (we're talking about a system that have been developed for 5-7 years with at least 20 smart developers where things keep changing/updated/fixed, etc). I think you're stretching that point too far. Point #2 is more in the experience, a good developer (not necessarily great) can do this in any given day provided that he/she has the right experience. You don't know what you don't know => all others would either be 50-50 or intuition (a.k.a luck). Point #3 can be done by "good enough" developer as well. The fact that we have plenty "good enough" software systems that requires little to less maintenance running today is a proof of my statement. Point #4 debugging is about focus and patience. Give it to a decent programmer without time-limit and he'll figure it out, eventually. Point #5 any decent developer who have good communication skill can do this. I think we are guilty of underestimating "good" developer and overestimating (or plain worshipping) great developer.