Most of code that "needs to be written" is just a copy of something standard, "Do X in the simplest way possible" code that doesn't need optimizations, and writing it by hand is just waste of time. AI is good enough to write megabytes of that code, since its statistically common and part of tons of codebases. Its the other half of code that AI can't handle, that you need to manually verify it doesn't hallucinate fantastic stuff that manages to compile, but doesn't work.