Rowling never fully understood or navigated the waters she dipped her toes into. JRR Tolkien would have either laughed heartily or wept heartbrokenly at her ignorance and ineptitude.

Heroes - proper, old-fashioned heroes - do their fated deeds, then die! They do not marry their school sweethearts and raise kids. They either die at the completion of their destiny, or are overtaken by tragedy in later life. Heracles, Pryderi, Rustem, Sigurd, Arthur, Elric of Melnibone, Frodo Baggins - all suffer heroes' fates. Fates brought about by a flaw in their character or a single mistake.

Harry fulfils some of the hero criteria -raised in ignorance of his heritage, mentored by a wise older man, subject to a fate he did not choose and cannot avoid. But he does not have the character of a hero, rather of a modern protagonist (he is actually based on James T Kirk). Thus his flaws are not fatal and he survives.

So the end of the story is only satisfying in the more modern, Disneyesque, sense. That is what reduces the story to average when it might have been worthy.