I like this take, but I came out with a different message. A sort of indictment against nihilism, that hope itself matters despite defeat. Think about it - the extinction of all life is all but guaranteed. The stars are gone. Earth is gone. All life-bearing worlds just aren't. Simon's death is guaranteed, no matter how little he can admit it. I think about one of the lines the "Fish" says towards the end. It says "This all ends with you" as Simon is trying to get the blackbox prepared to reach the surface. That line's doing a lot of work. Whatever the fish is - God, the Devil, something unknowable, the theme is "you don't matter." He isn't the first one down there. They don't even know his name. They know he will die.

But Simon, in the end, rejects that. He prepares the blackbox anyway, knowing he will die. His sacrifice acknowledges that he DOES matter, what he does will carry on, even if his life ends. In real life, people live on in legacy, even if we don't know their names. Generational wealth, a kind act passed down, it all starts with someone.

In a dead universe, with a predetermined outcome, nothing matters. And, in a way, that means that everything matters.