Intrinsically simple and straight forward problems are easier to secure even with mediocre or bad code. They've already shown that Opus 4.6 can find and report on very sophisticated security issues[0] so I'm not sure that analysis (and perhaps especially security analysis) is the biggest issue with LLMs.
Mind you, I'm not using LLMs for professional programming since I prefer knowing everything inside and out in the code that I work on, but I have tried a bunch of different modes of use (spec-driven + entire implementation by Opus 4.6, latest Codex and Composer 2, and entirely "vibecoded", as well as minor changes) and can say that for trivial in-house things it's actually usable.
Do I prefer to rewrite it entirely manually if I want something that I actually like? Yes. Do I think that not everything needs to be treated that way if you just want an initial version you can tinker with? Also yes.