Excel doesn't treat gene data as dates, it treats text input in certain formats as dates unless you tell it not to by explicitly specifying the data type. Scientists have a whole constellation of tools to choose from--various spreadsheets, Jupyter notebooks, R programs, custom apps written by colleagues, etc.--and each one will have a certain feature set that will have to be used properly to avoid errors. Excel is not "buggy" in this respect.

I will say, though, that I have been repeatedly surprised when creating large, complex models for others in Excel at how easy it is to have a bug in your "code" that isn't obvious. In this respect, it's a bit like JavaScript's philosophy of "don't crash or sound an alarm, just make your best guess and keep going." For simple things, this works fine, but for anything complex, I really prefer more "bondage and discipline" from the platform, so my potential errors are pointed out rather than forgiven.