Respectfully, I don't think it's insightful to point out that Excel is Turing complete. That's a technical curiosity, it doesn't inform our discussion here.

The boundaries of what we call 'software development' are fuzzy, but that's true for all sorts of things. Assembling a computer doesn't make you an electronic engineer, despite that you're building a complex electronic system. If a high school teacher comes up with a basic arithmetic question that, by coincidence, has never been asked before, the teacher still doesn't count as a research mathematician for solving it.