This isn’t a confusing lyric: the guy knows not what the song he is singing means. That is, he’s singing along with a song on the radio without understanding what the lyrics mean. Kurt Cobain didn’t like people like that, although he was open about the fact that his lyrics usually didn’t have any literal meaning. They expressed whatever conflict was going on in his head, but he didn’t tell stories in his songs for the most part. (Polly, About a Girl, and Lithium come to mind as exceptions.)
It’s true that a lot of rock musicians just don’t want to de-mystify their lyrics and a lot of songs don’t mean much of anything - but when their is a clear meaning or a story that inspired the song, you need to remember that song lyrics are not essays. Writing exactly what you think is not necessarily that interesting. Writing something that fits the music and that listeners can interpret their own way and find meaning in - even if their version is very different from what the lyrics mean to you as the writer - is art. Cobain could be a snob (and so what if he was?) but he didn’t like people who heard what he was singing without thinking about what he was doing.