Rick and Morty jumped the shark with the pickle rick episode. Not because the premise was unimaginably stupid--which it was--but because that was when Rick's power level got completely out of control. In the early seasons the heroes would have to run away from enemies or outsmart them... now rick just pulls a deus ex machina out of his ass every time and just mercs every problem before it even threatens to become interesting. An omnipotent protagonist does not make for a compelling story.

The fundamental problem is the same as Game of Thrones: they got too popular too fast and started pandering to their dipshit fans for fear of losing their audience. Art cannot survive under capitalism.