"Gut feeling" is not intended to be a source of evidence, here -- he's trying to describe a sensation that the audience feels. The sensation that, "this isn't

"Gut feeling" is not intended to be a source of evidence, here -- he's trying to describe a sensation that the audience feels. The sensation that, "this isn't as good as it used to be, but I don't know why." He's proposing that the cause (or at least, one possible cause) of that "gut feeling" is that movies are poorly lit.