"Additionally the original excel sheet made incorrect assumptions ... NOT speedy."

So...not as I described then? If you are evaluating assumptions and going back to the drawing board, of course it won't be speedy. The point is that if it's simply a requirement to be implemented as is, it is a quick and speedy process.

And it is. I mean, there are dozens of products that will automate the entire process it's so rote.

No but I don't think what you described exists but for the most basic scenarios.

And I absolutely agree. My point was that Excel workbooks exist in a no man's land, where untenable practices are allowed by necessity. When we transition away inevitably we add layers of error checking and validations and security controls and processes, etc, that turn a simple project into a monstrosity. But it isn't that Excel was efficient anymore than having the random cowboy coder throw together the most adhoc thing imaginable (but quickly) is efficient.