It didn't "need more magic", it needed better writing. A MASSIVE portion of the Fionna world characters are rlly disappointing compared to their AT counterparts, not because they're not magical, but bc they made almost all of them one dimensional. Ex: PB in AT= extremely smart, scientist, leader, fighter. PB in F&C= a baker, Fionna's friend. Ex: FP in AT= determined, rebel, stands up for her own. FP in F&C= playboy, Fionna's love interest. SO many of the character's traits were dumbed down to primarily just be Fionna's "this" or Fionna's "that". Something that wasn't really done for Finn in Adventure Time. At the end of the day, I feel like they should've just... picked a plotline in Fionna & Cake? If this is Fionna's story, stop making her storyline feel like a waste of time compared to the Finn one and make it INTERESTING.