Frankly i think they kinda ruined it with Prismo coming back.
I mean he is not that relevant of a character since they aren't doing episodes with him and you made all the sadness of Jake basically wasted time because of plot armor.
Hell you made the Lich irrelevant as well, in his campaign of doom he basically managed to kill nobody.
.

Yeah, I don't disagree with you on that.... Prismo's death just absolutely floored me, and while I was thrilled to see him back, it did kind of cheapen the whole thing. I am looking forward to seeing where they go with Sweetpea, though. And I feel like Prismo might come up again in a big way. But...

That all being said, I've definitely been feeling a bit disenchanted with Adventure Time as of late.

The problem being they keep the status quo at every turn.

Nothing ever happens to actually shake the story around, that creates a plot, that makes the character goes "Oh we're fucked".
Everything is nice, every problem fix itself, nobody ever dies and those who do actually die didn't mind dying in the first place.
It's boring, you know nothing will actually shake the fundations of the whole thing.
Even worse now stuff it's focused on drama than actual adventures, drama that of course goes nowhere because of status quo.