...a lot of you are reviewing this far too seriously and definitely a bit overly critical.
The show is 20 years old. You are more than likely (most of you, anyway) having fond memories of when you were a child 8 years ago and thought it was the funniest thing ever. Sadly for you, the show has progressed and is done more around subtle adult humor these days. It's still funny, but you have to have a fine sense of humor to spot it.
The Simpsons is just not in-your-face comedy like it once was. If it were, you would complain about that as well.
Now, with that all said... I will give you that this was not the best Halloween episode they've ever done, but it is certainly not the worst. I've been watching this show since it was a short on Tracy Ullman's show and it's as funny to me now as it was then. It's grown with me and I've grown with it.
So if any of you armchair critics thinks this show is so bad, stop watching it or become a writer and see if you can do better.