It's not flashy movie that romanticizes the humankind's struggle against nature. It's a pseudo documentary of what can happen in such a disaster. There was an attempt to introduce some of the cultural conflicts and bigotry that is still quite the tapestry of middle America.
The movie does not attempt to embellish too much and a few characters do show some growth. But mostly. it's just people as they are in a disaster and many walk away without any change in their whole humanity.
In trying to keep special effects to a minimum, and perhaps in an attempt not aggrandize tornadoes, the movie may not be as engaging. I think it was trying to be honest and too honest perhaps.