To add to what you said, you certainly need not understand Category theory in order to be effective as a functional programmer.
Category theory is a very powerful concept. Understanding elements of it will certainly open your mind to the fundamental nature of mathematics. But the essential aspects of it have long been mapped in to other, more accessible, theoretical frameworks. So you can usually get away with never knowing that subject :)
Category theory is a very powerful concept. Understanding elements of it will certainly open your mind to the fundamental nature of mathematics. But the essential aspects of it have long been mapped in to other, more accessible, theoretical frameworks. So you can usually get away with never knowing that subject :)