Everything you have described, apart from on-call, I think LLMs can/will be able to do. Explaining code, reviewing code, writing code, writing test, writing tech docs. I think we are approaching a point where all these will be done by LLMs.

You could argue about architecture/thinking about the correct/proper implementations, but I'd argue that for the past 7 decades of software engineering, we are not getting close to a perfect architecture singularity where code is maintainable and there is no more tech debt left. Therefor, arguments such as "but LLMs produce spaghetti code" can be easily thrown away by saying that humans do as well, except humans waste time by thinking about ways to avoid spaghetti code, but eventually end up writing it anyways.