Anyone who says they don't understand why this film has received such low reviews or negative comments has either never taken a film class, has no objective reasoning, or has the standards of someone who thinks Starbucks actually makes good coffee.
While Intrusion does have some good qualities to it, none of them will be found in its plot, writing, or acting choices. The film itself is derivative, and you could probably find 100 films just like it that are much better. The big "twist" is obvious fifteen minutes in, and no attempt at subverting our expectations is made. You may find such a predictable movie a bit boring and formulaic, especially since nothing about Intrusion offers anything different or unique as a thriller.
There are some beautiful shots of the surrounding landscapes within the movie, but they are almost lost when at key moments in the film, the camera becomes tilted so that the shot is either sideways or completely upside down. I suppose this was meant to help build suspense and lend credit to the genre the movie breastfeeds from, but it inspires physical sickness, not awe or appreciation.
The acting is sometimes very good, and at other times, odd to say the least - something I attribute to a lack of chemistry between the two actors themselves. None of the dialogue in the film seems natural - between any character - and it's confounded even further when the main actress has some weird British accent even though in the film it is clearly stated she was born in India and then moved to Boston. (And the actress herself isn't English.)
Some actions of the characters don't make sense either, especially the supporting cast. One of the side characters who has a video tape recording of damning evidence, for whatever reason, has chosen to mail it to himself, or left it in his own mailbox for whatever reason - because you know, that's where I keep important things.
Even one of the main themes is illogical; that the the wife can't take care of herself because she used to have cancer before the events of the film. She has a successful career, exercises, drives, and can clearly support herself. As to why the movie leaned on the idea the husband was the provider and necessary to her survival, I cannot fathom. Nothing indicated she needed to be saved.
Ultimately, this movie deserves its low rating, because in a world over saturated with film, there needs to be a way to look at cinema with some sort of agreed upon lens - something that says, "Yes, this move did X, Y, & Z very well, while this other film did not," and then list those reasons. We can't just give a movie a pass because it gave us something to do for 90 minutes and we're too stupid to watch anything better.
But then again, some people think Starbucks makes good coffee. What do I know. I'm just an guy who had an extra ten minutes.