Slate's Joseph Lapin suggests a way of making the Simpsons "relevant" again: The Characters Should Start Getting Older
[Killing off a character is] just a temporary fix: It will not restore the show’s reputation as innovative or groundbreaking. To reclaim that type of territory, and reestablish its hold on the American zeitgeist, The Simpsons needs to think much bigger. So here is what I’m proposing: The Simpsons should break free from its static biological present. The characters need to age. Yes, a cartoon, a 2-D world where the laws of nature are constructed in a writers’ room, should suddenly be forced to carry, like Homer chained to the “Stone of Shame,” the same burden all humans are forced to carry: growing older.
No. It's already done. They should just end the show itself, before it really starts to stink.