It's not really that this movie is inappropriate in terms of content for teens, but it doesn't really seem to be out to do much for them except to tell them that life will beat you down, and you can tell yourself you can beat it all you want, you ultimately can't. I'm now going to tell you the ending. And no spoiler alert, ’cause I'm saving you time:
Llewyn doesn't accomplish anything. He goes to Chicago, gets rejected, tries to apply to the Marines (think “Captain Phillips”), gets rejected there because he burned his pilot's license, then goes back to where he started at the beginning. That's basically it. The movie had you spend a great deal of time getting involved with his story and hoping he'll get out of the slump he's in, simply to bottleneck at a cheap ending in which absolutely none of that mattered. In doing this, the Coens broke a cardinal rule of storytelling they had not broken before: Don't have anything in the story happen by accident. The whole plot is treated as an accident. As a result, the film comes across as much creative and technical mastery, little (if any) point. “You can't short-change yourself.” Unfortunately, Llewyn ends the movie where he started: Thinking there's little, if anything, TO shortchange, when the audience sees countless things.