My wife said it well: it's like listening to the show except you have to watch it.
There is something attractive in the movie (and in the radio program): Americana. Things that are ours are always attractive. How could it be otherwise? They would not be ours if we weren't attracted.
Gospel music is prominent in the film. The gospel music is moving and powerful because it is American. The religion or doctrine that produced those songs, however, is not prominent. In fact, the dead woman who acts as "angel" is a comfortable/comforting distortion of the Christian doctrine that brought those songs into being.
"Comfortable" is a key word. The messy questions about where America came from and where those hymns came from is glossed over. Here we are, listening to familiar things, joking in a diner.
Comfortable. Not strong. Not compelling. Attractive.