This is up there with the worst endings in TV history. It's like the writers sat down with 7 pictures of the suspects and just pulled one at random. There is no story in this episode. Bruno Heller was telling the truth, Red John is just a regular guy. No charisma, no smart talk, no explanation what made him to become Red John, no connections to anything in past episodes, no nothing, just a guy who is killed by Jane and that's it.

You could actually replace Red John by any character who was ever for more than 10 seconds on the show and there was nothing that needed to be changed in the episode, except replacing the Red John actor. Everyone would fit. It was completely generic.