Being unable to work on a codebase without AI is not necessary. Working with models you can fit on consumer hardware is already significantly more productive than rawdogging code. It's similar to "you won't always have a calculator with you" from math teachers, see how that turned out.

A way bigger problem is a codebase that you can't effectively work on with AI, which is a lot of legacy humanslop. And things that make a codebase more suited for AI, like documentation that provides relevant domain knowledge and context for requirements, automated quality control, and test coverage, also make a codebase easier to work on for a human too.