I know and I stand by opinion of it: it's a stupid, flimsy excuse. The filmmakers put it in there because they needed to keep the action on their set (understandable) and they couldn't think of any interesting way to do it (lazy).
It's called suspension of disbelief. They needed the characters to stay in the house so they came up with a reasonable reason why they couldn't leave, or why leaving wouldn't serve them any good. It's a reason that makes sense in the context of the movie we're even given an "expert" in the movie to verify it for us (it doesn't matter that they didn't check with other "experts" the movie served us one and we're supposed to take what he says as gospel.)
Sometimes when people watch movies they take it too much into real life. In real life, yes, one would probably call other psychics or "experts" to fix their situation we don't have that luxury in a movie. All the movie needs to do is present its audience with a reason why the characters cannot leave, this movie did that. They told us right out why leaving wouldn't be of any help to them and they gave us an in-universe "expert" to verify it. The movie did its duty to suspend the disbelief.
If it didn't work for you then maybe you expect too much. I, for one, wouldn't have enjoyed this movie as much if it was more about them talking to various "psychics" to solve their problem or felt that if they left now the "demon" for the first time in 20 years would leave the girl alone.