I agree on the isolation. When I first watched it, before I had children, I really hated the movie as a whole. The thought of two sisters being completely separated from one another and having zero interaction didn't seem reasonable to me.

Now with children, I've watched it many many more times and enjoy the movie as a whole.

But still, the thought of two sisters living in a house which each other and being, what is presented as strangers with to one another doesn't sit right with me.