Function, yes. But are they happy? Were they children having to make these decisions? Your argument, while valid in some respects, doesn't make sense when applied to the issue we are discussing here- whether or not it is possible for several young teenagers to be mentally affected by war. A Flag Officer is trained. Guided. Briefed. Jake, Marco, Rachel, Cassie, and Tobias were thrown headfirst into a war, all while having to learn from experience, with very little help. The two aren't comparable.
There are a lot of people who are severely depressed, fighting wars or not. Does that mean they deserve to die? And I seriously doubt anything can prepare you for war, no amount of training can mentally save you. And for a group that wasn't mentally trained, briefed, and guided, they did better than almost any military leader I have ever heard of. But he's depressed because he made the large majority of decisions correctly and thus doesn't deserve to live I guess.
This entire time, I've been wondering exactly what it is we are debating here- now I realize, you completely misunderstood what I first said.
Allow me to clarify the difference between my saying that they "had to die" with they "deserve to die".
From a simple literary analysis, my absolute favorite endings are the ones that are, perhaps, least often seen. True tragedies- the antagonist either lives or dies, but the protagonist must suffer a tragic death. KA is the only author that I have read that not only had the courage to do that to her characters, she also does it within reason.
Obviously the most basic story has a beginning, a middle, and an end. A story is not truly over until the conflict has been resolved. The conflict cannot be resolved if characters are still dwelling on the past.
Look at it this way:
If Rachel has survived the war, she would have come out of it broken. Perhaps not permanently, but her insanity was accentuated for a reason. Or rather, more than reason. Without Rachel, it would have been impossible for Jake to kill Tom. As Jake points out, Marco and Cassie would have refused. Ax and Tobias were needed. Rachel was war-crazy enough to do the job. She loved the battle- and they worried what would happen to her when the battle ended. So in a kind of
"deus ex machina" way, that problem is solved when Rachel and Tom kill each other.
Had Rachel survived, Tom would have survived. Tom's yeerk would have survived. The yeerk's plan would have succeeded. Jake and the other Animorphs would have even more to deal with. And even if they won that particular battle, and Rachel survived, the conflict would never truly be over because Rachel would miss the fight. Perhaps she would find an outlet- as is human nature, she might pick fights just for the fun of it. But as is an even stronger human nature- we just don't let things go!
Tobias, one of my favorite characters, is stuck with an even more unusual situation- know he doesn't belong anywhere. Without Rachel, he is lost. He has no true family. His alien family is dead. His human disappeared. (Does anyone ever wonder what happened to his cat, Dude?). He could possibly trap himself in human morph again, but then would he be a human, stuck as a hawk, stuck as a human? And to have all that power taken from you- it is perhaps like seeing, then becoming blind. Like being able to walk, and suddenly you are immobile. That is something you would dwell on. A lost love, a lost power, a lost family. There was way too much for Tobias to deal with for him to not dwell on the past.
Marco, another favorite of mine, has almost the same problem as Rachel. He has few broken family ties, despite having his mother enslaved by Visser One for so many years. And yet, as Hylian Dan states- he finds himself completely detached. Bored. Tactically, he has nothing to do. A simple war would seem simple- and since his main skill was thinking logically, there are few things that someone with that much logical experience can do. Extreme intelligence from any angle is difficult to live with- Marco had an overdeveloped ability to think logically. And logic, when overused, will drive a person mad. IE: He was bored, and would always be looking for "one more adventure".
And Jake. Oh Jake. It took me several days to get over Jake. Jake, the thirteen to sixteen-year-old kid who has to make all the tough decisions- including the decision to kill the brother he had been fighting to save for three years. Jake, who never even gets to speak to said brother before his death. Jake, who knows the only way to stop his brother's yeerk is by sacrificing his own cousin. Oh the brilliance! When I realized what KA was going to do with him- well, I got very excited indeed
.
You see, so few authors have the ability to write a true final ending. Some don't wrap up enough, while others wrap up too much. KA knew her characters well. She knew who would endure the war and come out okay. Though I can't exactly explain why she chose to kill Ax- perhaps it was out of convenience, or I simply don't understand enough about Ax's character to realize what the reason might be. However, I do know that out of the six, Cassie was the one person who would hold on to nothing. Cassie would forgive and forget. She would be willing to co-exist with yeerks if she needed to. She would get past the war.
This is what I mean when I say they needed to die. For the series to truly be over, the characters had to let go of the conflict. Some of KA's characters were so strong, so determined, that they would never let it go. Others lost too much to forget. Oh brilliance. I was thrilled to finally read a book from an author who knew how to end a series.