To go a little further, there’s a very important character element in the novel about Expelliarmus being Harry’s “signature move”. The Death Eaters thought it was so bizarre Harry would use a disarming charm against Voldemort in the Goblet of Fire showdown, and believed it to be Harry’s “signature move”. So when Harry does it again against a Death Eater in the “Seven Harrys” bit in the opening of Deathly Hallows, THAT’S how they knew it was Harry, not Hedwig trying to protect him. Mr. Weasley then tells him he can’t risk have a known signature move, because it makes him predictable and would lead to his downfall.
Which makes the final confrontation so much better. After how dark of a place he was in between Sirius and Dumbledore’s deaths, up to the point where was trying to sling around unforgivable curses, he decides once and for all that attacking someone like that, even Voldemort, is not in is his nature, and fully and conscientiously adopts it as his signature. He warns Voldemort there’s nothing he can do to him, casts Expelliarmus in defense once more, and because Voldemort wasn’t the Elder Wand’s master and because Harry cast the disarming charm, Voldemort’s killing curse backfires on him like it did when Harry was a baby, and he dies.
It drove me ALL sorts of nuts they dropped all of that and went with “Harry and Voldy jump off a building, poof around a lot, and have a glow stick rave to the death”.