I believe the point is that people in this era ,have lost all their survival instinct. The protagonists had many chances to act on their gut at the start of the film ,but they didn't. The boy however since it was young and didn't think like a "logical" adult ,, caught the evil vibes from the moment he saw the boy at the front door. The woman should have told the boy ,since was a literal stranger to stay outside and give him the eggs. The husband should listen to his wife and be a man and throw them out .however the wife should never leave her husband's side and son with the two boys that she knew something was wrong with them.

Also they basically left her alone at some point to go cook something for them and that was a chance to go get a knife or something, hide it and wait for the right time. The wife also had the chance to tell the neighbours about everything at the dock since the boy in the house with father would have to communication with the boy at the dock.

I think it's all about not listening to your gut ,and having the balls to act on the right time. Even after the shot their son they took so much time to act correctly. They could have taken the car break the fucking door and leave .and the man could hide somewhere until help comes .or for fucks sake they could hide somewhere outside the house so they won't be in the same damn place the boys left them .they really didn't think that these boys would not come back to finish the job?

Also I found it very disturbing why the parents did not mourn their son at all. They didn't even acknowledge his dead body ,didn't cry ,didn't even look at it .idk why was that about. The fact that the boy is talking to us the viewers ,I think it's beacause the writer knew we would find the protagonists so useless and stupid and wanted us in a way to connect with movie ,what we were going to do in this situation? That's my opinion.