Developing forces that work against a character is just as important as developing that character. On Californication, the two are inextricably connected. The main force working against David Duchovny's Hank Moody is himself. Just when he gets a chance to right the perpetually sinking ship of his life, he gets too drunk, too horny, or too sarcastic, and lands himself in an even worse situation.
A couple seasons of watching Moody flounder were delightful, but at a certain point you have to ask, what's going to change? The show has always been able to find new and exciting ways for Moody to get laid, they haven't been as successful in coming up with new and exciting ways for his character to evolve.