In that case Excel's instant update and flexible (but quite powerful) formula scripting is often the best tool for the job because it means you remove the programmer middle man. I know some shops prefer to just teach the analysts how to write code.
Often this is down to people adding/deleting/copying or modifying rows/columns and forgetting to change cell formula.
So, in theory you can modify a workbook and get instant results. In practice this seems to be nearly impossible to to get right.
In the end I'm personally still in favor of Excel because it has a much gentler learning curve, though you are right that bulk operations in Excel are ripe territory for errors. I don't think it's "nearly impossible" though, it comes down to following best practices the same way you would in any programming language.
I really doubt any major finance player allows someone to whip up a spreadsheet, plug some numbers in and start trading off that information. Excel is valuable in the early stages because it's fast, powerful and easy to collaborate in. Trying to eliminate it just because it's Excel is dogma.
Clearly you only stayed in finance for a brief time :-)
Your fin model has normal sanity checks and then functional checks.
And in the end the out put must be readable AND make sense.
And whatever bug you have is going to propagate down your projected time series.
Finance chaps use finance as their weapon of debugging. Sure mistakes get through. I’ve seen mistakes get through code as well though.
Also - analysts get fired a lot faster.