Also, I always think Turing Completeness is a red herring in conversations about Software Engineering. Turing Completeness is such a low bar, that it hardly factors into most conversations about the expression problem. It's most notable when the goal is to actively restrict completeness.
It's kinda like starting a conversation about birds and first establishing they have mass.
And I'm just pointing out that in this particular case, Turing completeness was very useful in decisively stopping what would have otherwise been an unending and inconclusive argument, and, regardless of whether or not it can justifiably be called a low bar, it was good enough in this case. Furthermore, It does the same in many other cases: for example, in the question of whether there are ISAs that are more computationally powerful than others. It seems to be, or at least have been, very useful in computer science even if it does not have much relevance to everyday coding, and it may not seem much of a big deal because the questions that it has solved are no longer (or never became) problems.
> In any Turing complete language, it is possible to write any computer program, so in a very rigorous sense nearly all programming languages are equally capable.
You seem to have more history on the matter than I do, so let me ask a question instead trying to defend that idea. Why did anyone think Structured Programming wouldn't be? They must have had reasons to suspect it. I also don't know much of the history of Structured Programming apart from "Goto Considered Harmful", so pointers would be great.