I think there's a lot of reason to what you are saying. The 4-5 amount of time to make the codebase readable resonates.

If i really wanted to go 100% LLM as a challenge I think I'd compartmentalize a lot and maybe rely on OpenAPI and other API description languages to reduce the complexity of what the LLM has to deal with when working on its current "compartment" (i.e the frontend or backend). Claude.md also helps a lot.

I do believe in some time saving, but at the same time, almost every line of code I write usually requires some deliberate thought, and if the LLM makes that thought, I often have to correct it. If i use English to explain exactly what I want it is some times ok, but then that is basically the same effort. At least that's my empirical experience.