Yeah that kind of stuff can definitely scare people away. I don't know what a monad is and I've stopped pretending to care. For me immutability and pure functions are the only important concepts; everything else is a bridge too far for practical corporate use. Still, I think that while null is commonly called "the billion dollar mistake", I wonder... I think that going back in time and making C# and Java immutable-by-default would have a bigger impact than adding null-safety. Maybe not a panacea, but FP does seem to set a pretty acceptable lower bound on how terrible a codebase can get in my experience.