Part I: Things which haven't changed, but don't work anymore
1. Marge just isn't a very good character
This was a fundamental flaw which was built into the structure of The Simpsons to begin with. Homer, Bart and Lisa are all brilliant, well-developed characters. Maggie is just a baby so she can't do much to begin with. But Marge... Marge is just a housewife. She's stuck in the past, stuck in a rut, and most episodes centering on her involve her climbing out of her rut, then falling back into it. There's no humour there. There's nothing to like. She's just the nagging good angel on Bart and Homer's shoulders. And that's a quarter of the main cast.
Interestingly, both Family Guy and American Dad - which rip off The Simpsons' "make fun of the traditional perfect American family" scenario - suffer from this same problem.
2. Same old setting, same old characters
For 350+ episodes and nearly two decades, nothing of significance has changed in the Simpsons universe. At all. Springfield and its inhabitants have all quickly become extremely firmly defined. They never change and never can - which, after so much time, makes them boring. And quite frankly, there's SO MUCH ROOM for things to change. The possibilities are endless and the existing archive of episodes is littered with wasted opportunities. What's Sideshow Mel's story? Why doesn't Herb Powell visit anymore? Just simply letting all the characters age a few years would do wonders! (And don't talk to me about those stupid episodes set in that bizarre Jetsons future.)
3. Exhausted format
25 minutes. Three acts. The status quo must always return at the end.
The plotlines that can fit comfortably into this timeframe began to run out somewhere around season five. By now they are essentially exhausted. The only way the writers have got around this is to compress longer plots into the time allowed, resulting in a show too fast-moving to have any harmony. The obvious solution is to move to longer plots - more two-part episodes, season-length story arcs, actual character development (see #2). I can only hope that the inevitable Simpsons movie takes advantage of the amount of time available to smell the roses, instead of working like a quadruple-length episode.
Part II: Things which have changed for the worse over time
4. Cold, artificial episode structure
Watch an early episode alongside a recent episode and you will understand what I am talking about here. The Simpsons used to have a wandering plotline. There were diversions - Bart joins the Boy Scouts (sorry, "Junior Campers"), as part of a primary plot line to get Homer, Bart, Ned and Rod stranded at sea, but before that we also get to see a few instances of Bart using his new trapping skills on Homer, just because it's funny. There were bits that were in there because they added scenery to the Simpsons family - there's an episode which opens with Lisa and her friends tormenting Bart during a slumber party, but has no connection to the main plot at all (well, Homer decides to go to the bar to escape the shenanigans, but no excuse was needed for that). The structure was fluid, imprecise, dynamic, organic - much like real life.
Now the plots have become so crowded (see #3), there's no time for indulgences. Everything, absolutely everything, follows the main plot line(s), to get us where we're going as quickly as possible, point to point. It's too fast, too rigid. Where's the soul?
5. Everything is played for laughs
The show was always comedy, but the jokes arose naturally - again, organically - from observational humour and witty writing. It wasn't really a sitcom in the traditional sense. At times it was even moving: take season two's "One Fish, Two Fish, Blowfish, Blue Fish" for example.
Nowadays the plot (such as it is, see #3) is little more than a support structure - a host body - for jokes. Everything is supposed to be funny: we've moved from an organic structure to a very pedestrian, monotonous sitcom-style joke/joke/joke/joke/joke grind. No pause, no drama, no feeling, no artistry - except in the designated spaces. You can't box stuff out like this.
6. No longer realistic
Don't burst out laughing at this one.
The Simpsons used to be about a family, and what they got up to. It was cartoonish and caricatured and unrealistic, but it was at least grounded firmly in reality. You could see your family in theirs. The things that happened were almost things that could happen to you.
Now watch "Goo Goo Gai Pan" (season sixteen), in which a Buddhist monk pulls Homer's heart out of his chest, then puts it back.
What happened to the family we loved? You know what I think? Somewhere along the line, they stopped being a family and started being cartoon characters.
7. Supporting cast no longer amount to anything
It used to be that there were lots of regular people in Springfield, with people like Sideshow Mel and Captain McAllister only turning up when it was a) relevant and b) funny. But there are no ordinary people in Springfield anymore. At all. Every crowd contains the same familiar faces. Every celebrity is Krusty, every salesman is Gil. And this cheapens them. Am I the only person who is sick of each and every one of these characters now? Sick of them all delivering exactly one line each and never amounting to anything?
Over time, these characters have all become zero-dimensional caricatures. We've got the hillbilly stereotype, the pirate stereotype, the stoner stereotype, the mad scientist stereotype, plus a dozen or so more stereotypes which The Simpsons created in its own right but are equally uninspiring.
But thing is, it wasn't always like this. In the season three episode "The Otto Show" we actually took a good look at Otto. He gained a personality. Whereas in season eleven's "It's A Mad, Mad, Mad, Mad Marge" he gets married, but we don't spend five minutes talking to him! Because the Simpsons are the only characters who matter, that's why.
8. Dumbing down
The Simpsons used to be clever. There used to be jokes you had to be concentrating to get. There used to be jokes you had to be well-read to understand. Parodies of stuff that half the audience might never have heard of, let alone seen. That's not it anymore. What do we get instead?
We get a thing I like to call Assertion/Confirmation Exposition. It goes like this:
Character: "Statement X is true!"
[something instantly happens to prove that statement X is true]
Look out for it next time you watch the show. It's everywhere, in every episode. Look out for the bit, let's say, in "The Girl Who Slept Too Little" when Marge says "We have to stop all this construction! The noise is jiggling my grapes to the bottom of the Jello!" - then holds up a Jello with grapes at the bottom to demonstrate. Why the visual aid? Why not just have the line on its own? Why not have a scene with the noise actually jiggling the grapes to the bottom of the Jello, then Marge seeing this and saying "We have to stop all this construction!"? Answer: because you're TOO STUPID to get the joke if it's presented with any subtlety, or so the writers seem to think. Go for earlier episodes and you'll see that it wasn't always like this. Go watch Futurama and you'll see that it doesn't have to be like this either.
9. Poorer acting
If I may be frank, I am of the opinion that, while The Simpsons did hit a very bleak and genuinely unfunny spot a few years back, a lot of jokes in the show currently are still funny... on paper. Watching the show, or running through the lines again in my head certainly raises the "joke" flag; it merely fails to make me laugh. Whereas writing them down for later quotation seems to improve the humour value.
I believe that this is more than slightly due to the voice actors not putting the effort in that they used to. I wouldn't hold that against them, if they believe the show has gone down as much as I do.
10. Not funny anymore
As one quick example, here's Assertion/Confirmation Exposition's evil twin, Assertion/Contradiction Humour. Observe:
Character: "Statement X is true!"
[something instantly happens to prove that statement X is not true]
This formula finds itself used, at a rough estimate, about a THOUSAND TIMES during the course of The Simpsons. Why am I angry about this? Because it's the very definition of unfunny. Jokes are funny when something unexpected happens. After more than a decade and a half of this same joke being used over and over again, I don't know about anybody else, but I can see this one coming.
More importantly, it, like Assertion/Confirmation Exposition above, gives the audience no credit. Jokes are funnier when you need half a brain to spot them. This, on the other hand, is just writing the joke on a placard and jamming it in the viewer's face. "HEY! YOU SEE THIS? THIS HERE'S A JOKE!" Assertion/Contradiction isn't necessarily a bad way to get comedy, it's just the juxtaposition of the two events which is more lame and predictable every time. The formula becomes infinitely funnier by simply moving the contradiction elsewhere - much later in the episode, for example, or perhaps earlier in the episode, or even just not overtly stating it at all - just making it clear from what we already know about the Simpsons universe:
Martin: "What is the matter with you?"
Bart: "It's my dad. Lying there on the couch, drinking a beer, staring at the TV... I've never seen him like that!"
All the rest of my grievances feed into this one. Lack of realism makes the otherwise outlandish seem pedestrian and unfunny. Lack of wit is a consequence of dumbing down. Stale settings, over-used characters, manic plots, unenthusiastic portrayals; all these things add up to one thing. The Simpsons isn't funny any more. And it hasn't been since... well, I draw the line at the beginning of season six, but, quite frankly, pick an episode.
Conclusion - can The Simpsons be saved?
I believe that the only way to make The Simpsons into a truly great television show again would be to bring in some sweeping changes - most of which I have detailed above. But there is a drawback; the inescapable fact that, if we're honest, essentially everything you could possibly do with the cartoon family scenario has already been done, if not by The Simpsons then by some other television show.
Brave and intelligent writing could get around this, but, let's face it, those of us who think the show even needs saving are in a minority. The Simpsons will not be saved. I have long since cut my losses and started watching Futurama. David X. Cohen is my master now.