I know just what you mean about the World Cup (and indeed about several other scenes, subplots, characters and situations), but the film was already over 2 1/2 hours long -- adding even one more thing would have shoved it over the length where theaters have trouble getting in more than one show a day at a reasonable time. (It's a silly consideration, but it exists)

I thought the entrance of the two other schools was stunning, especially the contrast between the over-the-top romantic balleticism of the Beauxbaton students and the military drill precision of Durmstrang. And I loved the opening of the Yule Ball, where you think that Harry and Parvati are just fumbling their way through a standard waltz and then with the little lift you realize the whole thing, with the hesitation and the shifting arms, is all real choreography.