Crimson Foster’s review published on Letterboxd:
So... I really liked this film! One of the first things that really stood out to me when watching this was how good the cinematography was. The use of mirrors was fascinating. Near the start of the film, there's this shot-reverse-shot where Dakota Johnson's character is placed next to a mirror (allowing you to see her reflection, along with her), with her reflection being out of focus. And to contrast this, the next shot is exactly the same, with Mia Goth's character being placed against a mirror, but it's her reflection that's in focus. To me, at least, that personifies the idea behind the constant use of mirrors and reflections in this film. In that, once you're a part of this dance cult, you lose that sense of identity, you're just a reflection of your prior self.
The scene in which Tilda Swinton's character makes Johnson jump higher and higher shows how those in power constantly hold those beneath them on this, sort of, leash. And if those w/o power don't want to take part in the 'dance', then they lose the home, food and comfort of being someone's pet. Chloë Grace Moretz's character loses the home the dance academy provides because of this. She and the other nonconformists get incredible alternative; torture and being mutilated! Sounds fun.
I've looked at some other people's thoughts on the film, and I'm seeing a lot about how the historical-political setting (1970s Germany) is being seen as unnecessary. I don't agree with that. The fact that all this is operating in a country still recovering from Hitler and the Nazi's only adds to the themes imho. Although no one in the film directly makes this parallel, I'm going to suggest that the dance cult is a microcosm of Nazi Germany. Hitler came to power at a time when Germany had no real identity and rose to the top because he gave many people a sense of that. It's just that identity was a very specific thing, and if you didn't fit or conform to that, then he'd not do nice things to you. Kind of like the cult in this film. The torture, both the Nazi's and this cult inflicts on the nonconformists, could be paralleled against each other.