Lyric discussion by t4r 

Cover art for Not Gonna Make It lyrics by Presidents of the United States of America, The

They're mocking the people who told them they wouldn't make it.

They intentionally sound like a really bad band by messing up the beginning and starting over, and then missing lines (the correct lyrics are "drummers who can drum," only one of them says "singers").

The only line in the song that rhymes is the one about not knowing how to rhyme. They're saying how ridiculous the criticism sounds.