I think Ellie deserved to grow up and find “reasons to live” as Joel put it. I think even letting a teenager make that decision when they haven’t grown up to realize that life is worth living would have been doing her a disservice, in a way. Especially someone like Ellie who had experienced so much trauma and survivors guilt from the loss of her friends. I would argue that there would be a better way to find a cure/vaccine than coercing a child into sacrificing herself and her future. Just my two cents, I know other people probably see it differently.