Adventure Time often tries to have daring stories with huge implications and consequences for the long term, but they always end up retconning themselves for no compelling reason.

Example 1 (and consider these "spoilers" if you will): Root Beer Man. He supposedly… you know, died. Aaand he came back to life for the sake of making an episode.

Example 2: Lots of things related to Prismo, which is self-explanatory at this point.

Example 3: Finn's arm.

And so on, so forth. Basically, the image nails it right by having Gravity Falls and Steven Universe nag Adventure Time about it.

The way I see it, Adventure Time can be described with the metaphor of a net.

The repeated locations, characters and subplots form a lattice into which stories are dropped, and the looser the net, the more it can bulge so that more stories can fit and those stories can have greater flexibility without completely falling apart.

Adventure Time is reluctant to resolve subplots, kill characters and fundamentally alter locations because the writers are always trying to ensure the setting has the maximum capacity for storytelling. They once said they aimed to write 1,000 episodes. How much would they limit themselves by allowing Bubblegum to get with Finn or Marceline, or some other similar game-changer?