Adventure Time used to be special because the world feels like a fantasy, and I mean a REAL fantasy, it's like something created by the mind of a child or a world born from the chaos of many minds adding their own touch and creations in a single story, it was like a big playground for many authors, we may consider AT the real DIVERSITY.
AT was something else, but the problem with this show was the plot, the same thing that made it good "the chaos" brought another problem, a conflict about the direction of the show and its characters. In general there is harmony but if you study the structure there is always some kind of conflict. Should Marceline kiss Finn? Do they have that kind of relationship? Yes! No... Should Finn have a serious relationship with Flame Princess, YES! No... Should have a romantic relationship with PB? YES! No...
This indecision made of the show something that never really start, some kind of status quo. It wants to have a plot but it never begins, it wants to create a development for the characters but they never do. Clearly something is happening behind the screen between the writers and probably the network and it's something so worthy of study like the show itself. I really wanna know more about this soft conflict.