Cedric’s death did have its place in the series, and it was pretty damn significant, but I always tend to think of the what-ifs.
Cedric was a House Champion and therefore no slouch in the academic department. If he had lived long enough to see the Reign of Umbridge, it’s quite possible he and Harry would have been the main teachers in Dumbledore’s Army. Couple that with the fact Cho wouldn’t have to deal with all those EMOTIONS that really tore into her, she would have been much more grounded and outwardly competent than her book/movie persona let on. She was always capable of so much, but her grieving understandably reigned that part of her in. A graduated Cedric and Cho would have come back for the Battle of Hogwarts and kicked ass. Back-to-back. Search your heart: you know it to be true, and it is glorious.