thoughts on Safety Not Guaranteed (spoilers)

Aubrey Plaza stars as Darius, a magazine intern who is assigned, along with staff writer Jeff (Jake Johnson) and fellow intern Arnau (Karan Soni) to research a story about a man who has placed an ad for a time traveling companion.  Jeff is the one who suggests the story, and it seems the only reason he did so is because the story will lead them to a coastal town where he hopes to reconnect with an old summer romance.  Once there, Jeff and Darius take turns approaching the man who placed the ad (Kenneth, played by Mark Duplass) pretending to want to be his time traveling companion.  Kenneth is immediately put off by Jeff, who gives him the standard lines about wanting to go back in time because he thinks it'd be cool to see dinosaurs and gladiators and all that; Kenneth and Darius, however, get along well, and she begins preparing for the time travel adventure with him.  She at first assumes he's crazy, and at one point thinks he's just flat-out lying about some of the things he's told her, but she grows to like him and begins to think maybe he's not so crazy.  Because I feel like I can't talk about my reaction to the movie without talking about the ending, I'm just going to go ahead and give it away: the movie ends with Jeff, Darius, and Arnau discovering that Kenneth really has made a time machine, and then with Darius boarding the time machine with him and the two of them disappearing.  Seriously.  That's how it ends.

Here's why this blows my mind: I never for one second thought that Kenneth had made a time machine, or at least not a working one.  I didn't think he was lying, exactly; I thought, based on stories that he told Darius, that he dearly wished he could go back in time to stop a particular event from happening, so he'd convinced himself that it was possible.  Darius has an event that she'd like to stop, too, so I thought part of her also wanted to believe him.  Because their story is intercut with scenes of Jeff reconnecting with his old summer love (Liz, played by Jenica Bergere) only to discover that she is still viewing him as a summer fling, and therefore a temporary part of her life, I thought this was a story about wishing that you could go back and be with the people you loved at the last time your life was really good, only to realize that that's not possible.  The fact that it seems that Darius and Kenneth really do travel back in time, however, suggests that maybe it is.  We don't really know, because we don't know if Darius and Kenneth are successful on their journey.  So...I'm not really sure if I get what this movie was about.  Also-- and this is perhaps a nitpicky point-- I don't really understand what kind of a magazine would pursue this story in the first place, and I don't believe that it would pay three employees to stay in a hotel and investigate this for more than a couple of days.  I don't know.  The performances were good and I had an okay time watching this; I just don't think I get the takeaway, or even know if there is a takeaway.