>>150879574
>Pen stepped down as showrunner halfway through Season 5 to work on the movie that was supposed to be
>Movie gets cancelled, gets rewritten into an episode by Moynihan

>>150242227
You should stop if you feel like you had enough. If you start losing interest in the world and its characters then there is no point in going ahead because nothing that is revealed in the end will matter if you are already bored. There is an overaching story, but most episodes are self conclusive adventures, it only matters for the season finales. Aside from the tonal shift post season 4, what I see most people having an issue with is that later there is some character assasinations, where characters that are seem as good do certain unlikable things, which can range from upsetting to awkward, but I never saw them as unnecessary for the current conflict, as most characters aren't even human and the human is an immature child. But I want to fuck Princess Bubblegum so maybe I am just not a good judge of character.
Tl dr: it is a fantasy show about a fantasy world from beginning to end, but it starts funny and silly and goes emo and silly in the end.