The main problem is that a complex spreadsheet is just code. Its a bundle of logic and data. That's code.

If the business stakeholders can edit said spreadsheet, they can code. Not well probably, but they can.

So, theoretically, they should be able to open a python script or whatever and hack away. A lot of calculations are actually much easier and straightforward in a real language as opposed to Excel.

But they won't, partially because developers would never let them.