Are management courses useless? As a business students I have taken tons of management courses - from marketing theories to company strategies to human resources. But I feel I literally got nothing out of them. What we have done is just to study by rote, sit for exams and forget 99% of the content two weeking later. Are they useless or should I have studied them in the other ways?

Here is a bit of my thought: let's take Cousera as an example. It offers degree courses in business, by completing which you could earn a diploma just as on-campus students do. However, they are video-based and lack interactions among students themselves and between professors and students. More importantly, you cannot network as those actually studying on the campus do, which renders them even more useless and in reality these types of degree are not even half as valuable as a full time on-campus degree. So, let's say, if management courses are really useful, why do online degrees still have not got recognition from the industry?
I won't comment on whether management courses are useless. But the way you approached them certainly made them so. Learning by rote the day before the exam and forgetting everything afterwards is a complete waste of time, unless your one and only goal is to get a degree at the end. If that's your only objective, then any course you take at the university is useless, really. If your objectives include learning, though, then you did a pretty poor job at it, and that's mostly on you. Yes, a bad course does not help. But there are plenty of things you could have done to make use of the lost time. Interact with students, ask the professor for more reading material, look for it yourself...