That said, while they do use some complex formulas, they don’t use any VBScript or other such madness.
Complaining that your custom MSFT/VBScript stuff doesn’t work, so you can’t migrate — it sounds to me a bit like “We’re stuck on Oracle and can’t move to PostgreSQL because we decided to use a lot of Oracle magic stuff that doesn’t work anywhere else”.
This is classic vendor lock-in, which I tend to view as a business risk best avoided. There really is no option except to recognize it as technical debt and find time to dig yourself out from it.
When your only option for “Business Function X” limits you to a single vendor, fix that first.
Oracle and Microsoft Office are global standards. The world uses them. Our civilization relies on them. If alternatives such as PostgreSQL and LibreOffice are not 100% compatible with these standards, they are lacking in functionality.
Oracle's definitely a standard in companies of a certain size and pedigree, but it's not even remotely as ubiquitous as Office, which is both a business and consumer product.
Good business is about managing and understanding risks, and not about eliminating them at all costs.
But when the only thing holding you back and locking you in is your own company's internal vendor-specific tooling/infrastructure, the argument doesn't hold as much weight.
fwiw, I have never received an Excel spreadsheet from a vendor/partner/customer that I could not open and work with in LibreOffice, re-export to Excel and send back to them.
And since Excel is the de facto standard, shouldn't Libre Office offer a 100% compatibility to whatever Excel has if it wants a piece of that market share? Also $150/year for something that does it all and just works it's really not much. The same reason why we don't ask how much Visual Studio Enterprise costs or IntelliJ products even if you have free alternatives.
Anyway, it’s a risk like any other, and it may often be worth it. The alternative of switching to libreoffice is not free, and can truly be more costly than some office licenses and the risk that Microsoft will drop or fuck up excel (which most consider low)...
Personally having earnestly tried to do some complex work in libreoffice calc and running into just bugs and poor polish (error handling anyone?), it is not an experience I elect to relive... I still feel locked in to Excel as my life is too short to waste on the inferior product.