There are many subjects that intermix with emotion every day. In that sense the human isn’t naturally a one subject at a time being.
A song can have multiple subjects intermixed, maybe even considered mini-dialogues, and or small reflections of many moments, triggers, feelings, messiness which best depicts the human experience.
Is this format too difficult for the listener?
It’s up to the listener to decide the level of openmindedness they wish to exercise. If the artist wishes to exhibit a multi-topic piece it must be broken down into parts like any machine. A song with it’s parts can be accepted as confusing if confusion is the emotion, or even state the writer is in.
Is confusion un-relatable?
Confusion is only there if communication isn’t clear. A song is in itself an invention, but it does need to communicate musically, and lyrically a purpose. If the purpose is to have no purpose than the listener can open or close their view, and stop the song. But how could the opening of their view change the process of human evolution and thinking?