Which part? I think even John Carmack in the video talked about the upfront thinking required for FP. If every CS student learned category and type theory like

Which part? I think even John Carmack in the video talked about the upfront thinking required for FP. If every CS student learned category and type theory like they learn complexity theory; and FP compilers could optimize type classes and all the object creation, FP would definitely be more widely used. But, yes, there is definitely a cost to picking up FP today in almost any domain, but it's getting lower.