Kinda? The new Spongebob sucks hosewater. I wonder what happened. We still watch it when it's on, but we don't tivo it anymore.
It's just the natural life cycle of a Nickelodeon show: the first season of Ren and Stimpy was brilliant, then some dolt on the writing team decided the gross-out aspect of the humor was what sold and it turned into trash. Invader Zim, the best show they ever had, got cancelled outright.
It makes one wonder about the management practices at the network: they keep starting winners only to kill them. (And it's not like the medium has anything to do with it: in Japan popular anime franchises can keep going for years, sometimes declining in quality, sometimes not.)