The myth that we've been shipping perfect code for years, but you can't trust LLMs, is just subjective blindness. People can't see the issues that they can't see, definitionally.

You can absolutely use the exact techniques we used to use in "the old days" to produce reliable code with LLMs generating most of it. The issue is, it's really not a lot less conceptual and intellectual effort than in "the old days", at root. You speed up the programming part, but the rest is still a hard slog, so nobody is out here doing really thorough testing in ways we used to dream of.