Adventure time is pretty much what childhood feels like in an abstract cartoony sense, there's rules and logic to the world but it seems to just change and be flipped on its head randomly and everyone else seems to know it before you do, there's so many different types of people and places and concepts you've never seen before and you learn something new everyday
As the show goes on we see how Finn grows and learns in the world and we actually grow and learn along with him because we don't know this world either, because it's so different to the real one!
There's crazy tragic things happening all around him all the time and he can't help but see them through the lense of a kids perspective, and we can't help but see them through the lense of a kids TV show, it can't be that serious right?
The best example of this of course is the Ice King, he's a walking tragedy and a lot of people who grew up with the show (I watched it later on) didn't know how tragic his character actually was because they were just like Finn, kids experiencing the situation placed in the middle of this super silly world!
I don't know if adventure time being kind of a simulation of childhood is intentional or not but that's what art is for I guess, it changes for everyone who sees it
