"Wake Me Up When September Ends" was written by frontman Billie Joe Armstrong about his father, who died from esophageal cancer when Armstrong was 10 years old. Armstrong at one point dubbed the song the most autobiographical he had written to that point, considering it "therapeutic" but also difficult to perform.
"Armstrong has expressed his displeasure with the memes and has joked about wanting to write a sequel song in response called 'Shut the Fuck Up When October Comes'."
Yeah imagine performing a song about how hard it is to remember the anniversary of the most heartbreaking death of a loved one you've experienced, and then everybody makes a joke about reminding you of it for the next several decades.
To most of us it's about the time passing and the innocent never lasting (which I always assumed is a similar idea to "why do the good people always go first".).
That being said, if we stop joking about serious matters and just take everything seriously - whether it's intended like that or not - we're fucked.