This is in many ways a competently executed and stylistically interesting movie that is ruined by its single, simplistic theme: men bad.
To be clear, I think the subject matter of women's struggles with toxic men is worth exploring, it's just done in a very black-and-white way here. The protagonist is traumatised by an ex and sees all men as being the same, but instead of processing her trauma and re-learning nuance, the movie quite literally concludes with her accepting that her ex was, after all, bad. This movie is filled with scenes that would be fair enough in isolation, but it all comes together for a really toxic and braindead takeaway.
It has some mindless entertainment value if, like me, you enjoy getting weirded out by a pretentious, arthousy horror movie that offers something other than cheap jumpscares, but don't expect more than surface-level symbolism which beats you over the head with its repetitive message.
The people giving this movie five stars are evidently operating under a different definition of the word "deep". There are indeed some details to pick apart, like the Green Man or the way people (or in this case, the titular men) perpetuate cycles of abuse, but none of this is as intricate or nuanced as other reviewers would make it out to be. I would say it's like the director knows how to use interesting symbolism, but has no idea what to use it for and ends up communicating the same unnuanced message in a hundred different ways. If a being from a parallel dimension saw this film and had no other context for what humans were like, it would assume that the males are all devils who exist only to abuse, and then minimise the abuse of, women. If that message appeals to you, then I have no doubt that you'd love this movie. Personally, I found it trash.
Still, I feel that a one star review should be reserved for an all-round incompetent mess of a film, which this definitely isn't. The acting, cinematography and atmosphere are all pretty decent, and the one thing you can't say about the movie is that the climax was predictable.
I'll give it a 3/10. Acting good, but Men bad.