>Isn't the economics of maintenance and change shifted so much that accidental complexity isn't actually all that expensive/painful?

Not while context windows cause decay and larger bills.

The AI's max cognitive load C is larger than a human's, but if codebase size grows unbounded the minimum context needed for a change will eventually surpass C.

It is also a bad idea to let your codebase become only readable by a machine when we are still in the dark about the role machines and people will take in the future. What if you have to go back to manual dev in a now gargantuan codebase?