Music and culture are important when learning a language. Is this what you mean by Mukimuki manmansu? I don't think you can learn much Korean from them, just vocabulary. They don't use many full sentences but I love them.
I don't see much like this, but its here. A lot of Koreans don't like kpop. It used to be around that time (2013) that I would play a popular video in class and everyone would scream in delight. Today I will get half the kids saying, "turn it off". They would prefer "real stuff" like independent stuff like Mukimuki than BTS.