He doesn't have anything to *say* about guilt or regret. He doesn't have an insight on it. He doesn't have a new way of making you feel something about it either.
It's on you to take what you already know & make meaning out of that.
I complained about how bloodless & frictionless the movie is: Nolan isn't making you look at *anything* that you would rather not think about. No, he's keeping you right in your comfort zone, thinking thoughts you've already thought.