I talked to the Rick and Morty artist. We actually hung out with the same group for the after party. We all followed each other around to 3 places and closed down 2 bars. I left him alone at the bars with the fanboy shit because he looked like he was trying to pick up girls. But he was pretty cool. People were coming up to him all night and he was doing pictures and drawing R&M on napkins and body parts and shit. I was disappointed he didn't draw on any titties, but hey, you can't win them all. At one point some rando told him that he loved Rick and Morty, but after season 3 it went to shit. His response was that S4 was a buildup to S5.
Anyway, the next day I asked him why the seasons take so long. He said it was mostly because of the animation schedule. All of the animators work for Adult Swim (he works for Rick and Morty, not adult swim) and they have a lot of shows to animate. So things get bumped around on the schedule all the time. He did mention there was a new contract that should fix that.
I also asked him how much Harmon and Roiland are involved in the show. He said they're heavily involved. They dream up the ideas and the rest of the team has to make them legal to show on TV.