People have seriously missed the point.

Rating: 9/10 (5 October 2018)

I have read a ton of reviews after watching this movie, and the conclusion I've come to, is people just don't get the point the movie is making.
**SPOILERS**
The movie isn't just about an alien life form that has come along to 'destroy' us, it's about something more. It's about our understanding of existence and life and how our understandings are still limited by our own knowledge of the physical universe.
My field is sociology, and as a sociologist, my main mantra is that 'everything we know may not be true.' This is what this film highlights. Our understanding of the physical universe is limited by our own understanding of the basic laws of life and existence. Lena goes into 'The Shimmer' as a biologist that has a firm belief in what she believes are the cellular laws of biology and the universe. Everything she encounters in The Shimmer completely contradicts that. Little things such as the tattoo on her arm which is from one of the other members of their squad, show that she is not just 'herself' anymore, but rather, a compiled version of those she shared time with in The Shimmer. This is where the refracted DNA explanation comes into play from Josie, that states that 'it's refracting everything, even us.' Basically, Josie says that everything within this field is becoming a part of everything else. The bear contains Shepard in her last moments, the deer have flowers on their head, and so on and so-forth. This is why Kane is not Kane at the end, but still in essence is.
The deeper question this movie asks is: 'Is our understanding of the universe 'the understanding' or just 'a understanding.' It challenges you to to challenge your own beliefs of science and understanding and instead conceive of a possible reality in the future where none of the basic laws of science, biology, physics, hold true. There are some holes, but they are not major enough to affect the film in any great way.
As for the ending, Lena is Lena but she's not. Does that make her any more or less than she was? She is now the sum of others that she experienced her time with, so isn't this the same as what we do internally? Absorb things from other people and have that influence our lives to make different decisions. For me that was the point of showing the affair and how it lead to him going, which lead to her going, which lead to her lying and so on and so-forth.
This is my understanding of the movie, but as the film demonstrates, it may not be 'the understanding', as that is completely open to interpretation.
I think that's a great thing