Mike D'Angelo’s review published on Letterboxd:
A classic case of most people knowing too much about a movie in advance and consequently not seeing what's actually in front of them. To cite just one example, Eric Kohn called it "a structurally messy and confusing attempt at magical realism that doesn't find the clarity it needs to justify the rampant strangeness," which is inaccurate on four counts in a single sentence: (1) it's not structurally messy, at all; (2) neither is it remotely confusing; (3) "magical realism" does not figure into the film in any way; and (4) what strangeness exists isn't rampant. I don't mean to pick on Eric, either—just about everybody spent half their review or more complaining about an element that's barely even there. Admittedly, that element does not work. But it's like three minutes of screen time, total. Basically two brief dream/fantasy sequences (both in the last 20 minutes) and some interstitial Quay Brothers animation. Fixating on it and thereby rejecting the entire movie is ludicrous.
To be fair, some critics also found the central relationship unconvincing and/or undernourished. That's a perfectly valid criticism, except whaaaaaat?!? Gray's ability to coax natural performances from his actors is unparalleled—Juno Temple has never been anywhere near this relaxed before—and his commitment to emotional authenticity is, if anything, a little too extreme. The Exploding Girl applied that approach to subject matter so diffident that the movie was in constant danger of being blown offscreen by a mild gust of wind, but it serves as the ideal counterweight here, in the inherently tempestuous context of first love. Diane's ridiculous attempt to shave her vagina—the tender way it plays out, and the abrupt, anti-punitive way it concludes—is just one example of many. (Also of note: the sheer number of references to elimination throughout. In many ways this is a film about the effect of passion on the gastrointestinal tract, which to my knowledge is a subject previously unexplored.)
Another thing I cherished: Has there ever been a movie that introduced an identical twin and then deliberately made so little of it? The scene in which Karen calls Jack pretending to be Diane, while terrific for its own sake, seems to exist primarily to raise the possibility that it's actually Diane in the porn video, using her sister's name in an unfamiliar situation. Karen is otherwise never seen; one might fairly conclude that she's never seen at all. Indeed, if not for the fact that Diane's aunt mentions her, it would be easy to conclude that Karen doesn't really exist, so blatantly symbolic is her function. (See also: Jack's dead brother, Jack's facial bruise.) Like the monster metaphor, this would threaten to capsize the movie were it not so unemphatic; unlike the monster metaphor, its import is so glancing (there's no overt suggestion that Jack suspects anything, and the subject never comes up again) that it doesn't seem superfluous.
So yes, the monster stuff is silly and unnecessary—a bold idea that whiffed. And when you look past that, as you should, the film is "just" a touching, beautifully observed romance, with an ending that fails to achieve the catharsis it clearly aspires to. (Or maybe that's just my indifference to Yazoo's "Only You" talking.) But then, so was Andrew Haigh's Weekend, and people went nuts for that. Moral: Do not attempt bold ideas that might whiff. You will be severely punished if they do.
TL;DR: If you go into this expecting a "lesbian werewolf movie," you will be sorely disappointed, and it will be your own fault.