Not Enough Suspense

In order to build suspense in movies like this you need to at least tease the possibility that the characters have a chance at surviving. It isn't until nearly the end of the movie that some sense of hope is introduced when the characters call 911. But the characters up to that point are left absolutely powerless.

There is no clear reason why they all disappear one at a time or why when some characters are left alone for a few seconds they don't disappear then and there but they do disappear at some later point in the movie. Not even a hint of an explanation is given so we don't really know how to feel about their plight. It's just a thing that's happening and all the characters are completely passive observers.

It's like watching a man on death row being wheeled to the electric chair and then watching him get electrocuted. If you want to make that suspenseful then make the power go out or tease that there may be a stay of execution. Another analogy is that it's like a wind-up toy that is wound up (the premise of the movie is set up) and then released (the characters start disappearing) you know exactly what is going to happen and then it just happens. The only source of drama comes from the characters arguing and crying and that kind of situation has just been done WAY too many times in movies to really make the viewer feel anything.

In fact, this basic premise was already explored in a Twilight Zone "And When The Sky Was Opened" episode in which astronauts come back to Earth after they black out in space. Then back on Earth they start disappearing one by one. The Twilight Zone episode does it better because A) It achieves the same creepy atmosphere in like 1/3 the amount of time and B) the characters actually have something to DO. When one of the astronaut's disappears so does everyone's memory of him so the remaining astronauts are left to investigate this.