> Only when you implement by hand can you feel if the implementation of your design is painful or not, and only this signal can tell you if your design if truly good or not.

I think this touches obliquely on a point I keep coming back to, that one of the most important things a codebase does is to communicate ideas about how a process should work. Yes, it also produces some binary that runs on a bunch of servers or whatever, but that's a really temporary, ephemeral artifact. The lasting thing is the idea. Making your ideas (expressed in code) easy to understand, easy to work with, and easy to evolve in time is the art of software engineering. I 100% agree, from my own experimentation with LLMs, glancing at something a model has produced and checking that it has some test coverage isn't enough to know whether it's well-engineered. You'll only find out later when you try to work with the code.