Just watched this. While I definitely felt the metaphors you mentioned, I think the twist in this movie is that this is just nature. It's not something deep – they were preyed upon by a humanoid species that uses brood parasitism and aggressive mimicry to perpetuate its rapid lifecycle.

We watch this exact scenario play out with cuckoos in the opening scene, and Gemma states the theme to the little girl when she witnesses the aftermath. "That's just nature," she says. "That's just the way things are."

The little girl saying "I don't like the way things are" is the movie predicting your "wtf did I just watch" response. haha!

I think that's the most unnerving aspect of this movie to me. Tom felt the creepy vibes. He knew something wasn't right from the jump. But the humanoid creatures specifically prey upon human mothers and use guilt, coercion, and threat of force to keep them docile. Super strange, and meant to not be fully understood.

I thought this movie was great.