Its been a while, but isn't the main theme sexual slavery? I could understand why people consider that adult.

I admittedly don't have kids, but media is so saturated and oversexualized that I personally feel that thought-provoking fiction that dissect and critique urges are possible and good to explore at some point, in safe company accompanied with brief discussion. I'm certainly thankful I got offered these discussions in safe ways.

That said, Ex Machina might be a little intense in that regard, even though I seem to remember that the explicitly is mostly some nudity. It's a great movie, but probably not the first or fifth I would show a 12-year-old with the above discursive parameters included.

Perhaps the tenth or a six months on of watching and discussing movies and their depiction of life in an open way.

Not really? Main theme is a general intelligence that’s not aligned with you may trick or deceive you.