we know that, contrary to what Dumbledore promised, the Beauxbatons and Durmstrang and other magical societies didn't mean squat in the grand scheme of things. Umbridge didn't amount to nil, and Snape and his obsession with Harry barely moved the needle. In the end, all that
really mattered was breaking a few horcruxes scattered here and there, and a big fight that Harry won in large part on a technicality about Elder Wand nonsense. The house-elves, Sirius Black, Lupin the werewolf, Hagrid's giant relatives, the still-alive Grindelwald, Dumbledore's brother, Quidditch, Harry and Ginny's "romance"... all pretty much irrelevant by the time of the big fight, which doesn't even take place anywhere other than the same place 95% of the series takes place. It all boils down to a Voldy vs. Harry duel, and a crucial technicality.
Will audiences
really be jazzed to go through all of that nonsense
again?