(spoilers) Frustrating use of characters too disturbed to talk

I liked this movie, but found it frustrating. The endless scenes of questioning people who for one reason or another, would not talk.

It's hard enough to believe that Alex, with an IQ of a ten year old, would not be able to say something about what happened. I have a 10 year old child, but I'll let that one slide.

Then again, with Bob Taylor, who would not talk, I suppose for the same reason.

Then again, when Joy is found. She is at least 8 or 9, and she's been somehow been sedated at the hospital even though there is another child who's life is hanging in the balance. I am an emergency room doctor, and have never seen this happen. She is awake enough to say "you were there", but couldn't just add a bit more information for the police to figure it out.

I also don't believe that the father, who trains for survival, would have in any way put on those handcuffs and taken the sedative. Attacking her and hoping to survive a gunshot would have been the option he would have taken.

That being said, I liked the movie, mostly because of Jake Gyllenhall.

I think Enemy and Arrival are better Dennis Villeneuve films.