> The issue is not that nobody can hold these systems in their head, they can - they're just not paid to.

As of 2022, the largest transistor count in a commercially available microprocessor is 114 billion transistors[0]

According to cloc run against 3.13, Linux is about 12 million lines of code.[1]

Anyone that tells you they can keep this much information in their head is lying to you. And this doesn't even include how many lines of code are in a modern browser, which is still before we even get to a modern web dev stack. The total culmination of layers of code is impossible for any one person to hold in their head.

[0]: https://en.m.wikipedia.org/wiki/Transistor_count

[1]: https://unix.stackexchange.com/questions/223746/why-is-the-l...