I think the lyrics of many popular songs are somewhere between incomprehensible and vague. Lots of words that, along with the tune, convey some mood or set of feelings for the listener. But so many songs have no really clear meaning.
I guess Bob Dylan was the master of such songwriting. On some old Dylan album cover, the liner notes said that Dylan always leaves a space for the listeners to supply their own interpretation and meaning, and that that was the greatest songwriting.
And sometimes lyrics mean that the line below rhymes with the line above, and not much more. Some people have spent a lot of time trying to decipher the meaning of some famous songs, songs that probably don't really have a clear meaning.
Most lyrics are simple, and the meaning might be somewhere between simple and incomprehensible, but the general reading level is and probably has to be at grade school level.
There was a good interview with Geddy Lee (singer, bassist of Rush) about the whole song-writing thing. Peart (drummer) comes up with all of the lyrics. Lee and Lifeson have all sorts of tunes and riffs they have been working on. Then Lee tries to put them together.
He says often he can only pick a few things out of the lyrics that will work with the music. And he needs to be comfortable with the ideas expressed if he is singing them - he has to feel the words too in order for it to come out right. Once in a great while the lyrics and the music just click.
Lee said something to the effect of “I leave most of Neil’s words on the cutting room floor. But I know that he is just glad to have written them, regardless if anyone else hears them.”