New material is hard to come up with

Over the past few weeks I've been watching a lot of south park. Every single episode in-fact, and the film, and the pilots. Now there is an empty void in my life where the watching of south park used to be.
But one of the benefits of watching everything in such a short space of time is that you really notice the program evolving.

I don't think I'm alone in saying that the show has peaked already and is on the path to being shit (albeit travelling slowly down that path). And the problem lies in the lack of new ideas available to writers. Matt and Trey have done 17 series each with at least 14 episodes in each, (247 total as of writing); each of these episodes has a couple of plots to them on average and to keep that up is impossible. They've introduced new characters and shifted emphasis off of some (like Kenny) and onto others (like Butters) to create new story lines, but there are only so many ideas two people can have.Because of this, the last few series have had more and more 'current events' episodes appearing in them, the Wikileaks episode in particular being terrible.

Not this. But sort of this, politics has definitely played more of a role in the show recently, and the old Eric was more of a funny character than he is now.

So why have they done this? Because stuff that's actually happening is easier to make fun of than to think of your own events, and the jokes that are made can be less well done but still be funny as everyone can relate to what's going on more easily. Don't get me wrong, south park is still funny, but it used to be hilarious and it's not the same kind of funny any more.

But it's not just south park that's had to move away from broad topics and interweaving plots. Family guy has done similar things. Except they started off less funny and hence have become just plain bad, with new episodes being more like serious drama pieces with shitty (and predictable) utterances from Peter every now and then.
It doesn't help that South Park's humour mostly relies on it being shocking or taboo, it is it's own downfall in that respect, with each episode being similarly edgy and as such not edgy at all.

Yes, it's this picture

The characters have changed too, with Cartman going from a spoiled fat kid to being actively evil, and Stan's dad going from Stan's dad to a complete retard who is a bodged device for making any plot work.Although in this sense the show has morphed from being funny in a sick way, with a bit of dark humour in the mix, to just taking the piss out of people, with laughs coming through OTT antics as opposed to character relationships the viewer can relate to (like calling people fat and Jewish).

Another thing that I find lacking from newer episodes is the conclusion of the show. There sometimes just isn't one in shows that would normally have had one in previous series. This makes them come across as not really ending, you have the set up, then the mockery, and then nothing. It just ends. The whole 'I learnt something today' line would normally be quite insightful in episodes past and bring everything to a close.

But I don't think Matt and Trey should stop. I am a rare advocate for stretching out a franchise until is isn't good anymore (although the minute it stops being decent it should be stopped), and South Park is still good. But maybe they could get some new writers in once in a while.