> Excel still doesn't have any way of doing unit tests or confirming that the content is valid and as it should.

I make this point when chatting with new team members that say "let's just use X," without really understanding how X works, and I use Excel as the analogy. Most people know how to use an equation field. Most people don't consider writing a spreadsheet programming, but it is.

And just like other types of programs, you can have really insidious bugs, and you need to consider how you'll address those, or address changes in the underlying or internal components of the system.

A famous one is that floating point math in excel can give you different answers for "is this the same as that" depending on how you write the equation, for example.