We should steal The Declaration of Independence Microsoft Excel!
This has functionally already been done, its called LibreOffice Calc.
95% chance any business process that uses or touches Excel can be switched over to that with some minor tweaks, 5% chance someone might have to actually code some kind of custom API / batch file shim type thing, or its some stupidly niche situation where you truly are stuck paying your liscensing fer capitalism tithe to MSFT.