And the Xindi arc was pointless. Making the stakes the destruction of Earth in the PREQUEL was NOT good storytelling.
This cannot be expressed enough, and should be said until it is run into the ground so hard, it breaks in half.
Then what's the point of doing a prequel at all, if there's no tension or fear of failure for the chars, when we already know what's going to happen? What's the point of putting the chars into dangerous situations at all, if we know they're going to survive?
What is the point of watching a WW2 movie when you know the outcome? What is the point of watching Friends when you know they are still going to be friends the next day? Why watch all those movies that show you the end at the beginning?
A good show or movie can draw you in even if you know the end. I don't see the Xindi episodes being a waste because you know earth survives. The enjoyment of watching is to see HOW earth survives. It is the same way with thousands of other shows, movies and books. Enjoy the ride because when you reach the end, it's over.