First, please note that "failed predictions" in my list of arguments against Marxism. My list was, "
Evidence against Marxism involves mass famines, low economic productivity, failed predictions, and so on." In other words people who have attempted to apply Marx's theories have created disasters, places which follow his theories do poorly, academics who apply his theories to predicting stuff, get it wrong, and so on. As far as I can tell, any evidence-based assessment of Marxism comes up with a big fat zero.
Second, I wouldn't call myself particularly well-educated on Marxism, but I know somewhat more than the average person. And you're right that a Maoist is different than someone who studies Critical Race Theory, even though both may self-identify as Marxists. (And conversely both may NOT self-identify as Marxists even though Marxist thought has a deep impact on both.) However the "big fat zero" for Marxism includes, as far as I know, all derivative theories as well. But there are enough of them that I know little enough about that I won't recommend being particularly confident of that stronger statement.