Mike D'Angelo’s review published on Letterboxd:
Hate to say it but I think this would have properly devastated me had a different actor played the dad. (Actually, I'd like to retroactively cancel Captain Fantastic and have Mortensen play this role instead. In a less wacky register, obviously.) While I've liked Ben Foster in certain contexts—his brutally unsympathetic Lance Armstrong was 2016's least heralded great performance—he tends to leave me cold (dating back to Six Feet Under) when attempting to forge an emotional connection with his co-stars. Something about him just seems closed off, even when he's emoting for all he's worth. Maybe because he's often emoting for all he's worth. In any case, the father-daughter bond here, upon which Leave No Trace* almost wholly depends, never quite took hold, which leaves me admiring a film that I very much want to love. Certainly this confirms Granik as a major talent, committed to exploring the thorny relationship between character and environment. And McKenzie, as I'm sure everyone must have noted by now, is an amazing find...though you can't really know how amazing unless you hear her waxing dorkily enthusiastic about rabbits in her native New Zealand accent.
* Goofy confession: I went into the film cold, not knowing it's based on a novel, and when the title of the book appeared in the end credits, I abruptly burst into tears. Not really sure why, but it seems related to a similar experience I had with Dogville's closing-credits montage. That was a case of something very abstract suddenly becoming concrete; this time I think it was just the unexpected directness. I'm not gonna say what the book is called; you can look it up if you like. Doesn't tell you anything that's not right there in the movie itself. It's just...stark.