The assumption was that some engineers knew how each part of the system worked, or at least the system was comprehensible because it was created by humans for other humans. There were comments explaining difficult places, etc. With AI this assumption is broken. Now nobody understands how things work, and it cannot be understood in principle because the system is a mountain of slop created by some alien intelligence.
> Now nobody understands how things work
Well, the fancy calculators do. Yes, they still need guidance to keep from going off the rails. But, at least from personal anecdotal experience, I need to go spelunking into the codebase less and less over time. The agents and models really did just start to become that good.