Finn was there to self insert. But that's where everybody took a wrong term. You should've grown up with him. Realising it's not that important to get a girlfriend, all those shippers, all those Finncels - it's a coming of age story. He doesn't need any of his love interests, he doesn't need to be his big hero Billie and save OoO. And he kills Grassfinn (overcomming Marihuana addiction that pulls you back into a abyss of paranoia) comes to term with his mother and father etc. etc. etc.
you should be glad bout my dickflashing, not so much sword swinging one armed grown up boy.