This type of comment is always inevitable any time Simpsons gets mentioned in an online community.
No one denies that 3-9 was the golden age of the Simpsons. However 10-12 was the dark age of the simpsons. This was when Mike Scully ran the show; it had become very cartoony and "Family Guy"ish (maybe not so much with the cut-away gags, but in how it will compromise character integrity for the sake of a punch line). Around season 13 Al Jean rejoined the show as the showrunner, and the quality went back up. He was one of the original writers/show runners of the show.
So yes, Simpsons is not as good as it was in it golden years—I'm not sure if anything on TV is—but I think it's unfair to downright say it's bad now. It's a decent show, and still leagues better than Family Guy, at least. (I'm not sure why I'm suddenly comparing it to Family Guy—maybe it's because I hate Family Guy).
And before anyone points it out, yes, I'm aware of the irony that my signature comes from a Mike Scully episode of the Simpsons.