> I mean which task is so complex one can't just automate it with simple scripting and non critical if it goes wrong to the point of letting an AI LLM do it?

Many of the things that get to deal with unstructured human inputs. Translation, summarization, data extraction, etc. The choice isn't between "reliable code" and "unreliable LLM", but rather "unreliable LLM" vs. nothing at all.

But I think more important aspect is that LLMs are getting quite good at coding - meaning they can be used to automate all the tasks that you could automate with scripting, but it wouldn't be simple, or you don't know the relevant tooling well enough, or you just can't be arsed to do it yourself.

For example, I've recently been using GPT-4 to automate little things in my Emacs. GPT-4 actually sucks at writing Emacs Lisp, but even having to correct it myself is much less effort than writing those bits from scratch, as the LLM saves me the step of figuring out how to do it. This is enough to make a difference between automating and not automating those little things.