it’s precisely because software engineering is hard (not difficult, but rigid - objective) that makes it a good fit for LLM agent execution

Yes i think we're actually in agreement here. I said "hard" (not difficult) as a reference to "hard problems", a term that comes from complexity theory but is now commonly used to describe problems which can't be reduced to an algorithm or evaluated objectively, and thus can't readily be "solved".

Squishy subjects like music and sociology are full of hard problems, while solid subjects like math and coding are full of easy problems. Now the change introduced by LLMs is that as long as a problem is "easy", it can no longer be so laborious as to be impossible. Every software problem is solvable, modulo the effort/computing power you can spend on it.

Your job as a software architect / engineer is actually to find the easiest workable solution(s).

You also get bonus point if your solution is average (standard, unsurprising etc...), which makes it particularly soluble in LLMs which, by definition, can only produce output that is within the distribution of their training set.

As for relative difficulty, the “soft” fields have a very sliding scale for that with a lot of allowance given to newbies that isn’t accepted “at the highest levels”

That's not where i would put the difference. If you take a field like music, the problem is that it can't "just work". A nostalgic song may move the masses today but you can't say "okay we've solved nostalgia let's get to serenity next". Soon enough you'll need a new nostalgic song and by definition it will be out of distribution. You can't find it in a high dimensional representation of past music, and, well, you can't train on future data, so there is no way an LLM finds it and recognizes it for what it is.

with a high bar of standards required before publication and release, LLMs are a powerful tool that can accelerate many creative processes

I still believe they'll never amount to much regarding artistic processes, and not just for the reasons i already mentioned. To make something good you need to sit with it and walk with it and spend some time in it doing all the tedious little tasks until it really feels like home and you can express yourself in it. You can't achieve that if a machine speedruns all the little tasks for you.