My work has spanned almost all of the different examples you listed, and I don’t believe my ability to work in those topics or understand them was aided or help

My work has spanned almost all of the different examples you listed, and I don’t believe my ability to work in those topics or understand them was aided or helped by studying discrete math at all. (Note: you lump linear algebra in to the discussion but it is dramatically different than what is typically called “discrete math.”) Additionally, many of my colleagues on machine learning and intense distributed scientific computing applications that I’ve worked on have had zero discrete math education or self-teaching. I am more effective at engineering in these applications than some of these people, and less effective than others. Prior exposure to discrete math seems to have no effect.