Ok, I don't see how "one species dies and another lives" represents anything that is 'good'. It's just one way things could be. They could be other ways, and evolution doesn't show any preference for any of them.

What you're missing is that 'good' is defined with respect to a goal. From an evolutionary standpoint (whatever that really is), the complete extinction of all life is just one possible way things could be and it is as good as any other way things could be. From a human perspective, this is awful. As is any future where humans don't exist.