Cramer K.’s review published on Letterboxd:
Nostalgia is like a drug: some people can handle it in small doses and be perfectly fine, and some people can get addicted to it and really fuck themselves up. "Safety Not Guaranteed" is about people who binge on nostalgia like Jared Leto mainlining heroin in "Requiem for a Dream." It's a comedy, and very funny one at that, but it's still a sad, sad tale when you get right down to it.
Mark Duplass plays the most outwardly-damaged of the characters, as a would-be time traveler who seeks a companion to return to the past with him. Though he is sincere in his belief that he can undo past wrongs to save the people he loves, it's pretty clear early on that his real mission is to salvage the wreckage that his present life has become. Aubrey Plaza, Jake Johnson, and Karan Sani play three reporters who track down Duplass in order to debunk his Doctor Who fantasies, and all are in different stages of grief for the past. For Plaza, she finds that her spiritual pain aligns with Duplass', and the two develop a kinship that is the heart of the movie. But to me, the soul of the movie is Jake Johnson's turn as a jaded thirtysomething who has never really gotten over his high school sweetheart. His is the worst kind of nostalgia: the kind that can delude you into thinking that the salad days of the past can be recreated in the present. As "Safety Not Guaranteed" demonstrates in one of the most painfully honest scenes all year, it's this kind of thinking that leads you to propose to a virtual stranger and then end up alone, chugging a bottle of whiskey while driving a go-kart.
If there's a fault to this film, it's that it could have used an ending that was a little more ambiguous. By the last scene, I was much more invested in the characters' psychological growth than I was in any of the can-he-really-go-back-in-time hooha that the film threw at me. It felt disingenuous for the movie to replace genuine emotional catharsis with sci-fi tropes that didn't really fit the rest of the film. But this is just a slight misstep in a comedy that does a lot of things very well.