I think what helps make it a mess is that GoF really isn't so hot of a book, either. It was the series experiencing growing pains, I think. I mean, it came out fine and all, but it was really where the ineffective devices used thus far in the series drew attention to themselves. Allow me to elaborate. Sorry if this is a bit muddled but lol insomniac.
Even since reading the first book, I questioned the importance of the books' use of MacGuffins. And I don't mean in the plot. I mean useless plot devices, namely the prominence of Quidditch in early books (it never really has much purpose in the plots, although sometimes events that happen at games have importance), and the house points things.
In the early books, a Quidditch chapter was basically a sign you should quit reading for the night, because you were about to fall asleep. Not only are those chapters fuck boring, but the scoring rules of the game make little sense. So you have a shitty MacGuffin plot device, prominent and useless, and it doesn't even make sense internally. Unsurprisingly, the Quidditch World Cup in GoF pads the fucking book like a pillow filled with lard, drawing more attention to itself than ever before.
Similarly, but not quite as badly is the house cup/house points thing that is prominent in early books, but all but dropped by the time books 4-5 roll around. As near as I can tell, the only purpose this lame plot device serves is to add a bit to the conclusion of the first book; an extra hurrah for the ending. But the fact that it exists, that it is important in the first book and basically ONLY the first few books, is silly and inconsistent. The house cup is a big WE GOTTA CHEER FOR IT thing at the end of book one, but it means jack squat in the rest of the series? Lame. I understand that JK made the right decision in getting rid of this, but the fact that it was ever in has me smh.
Also, the Tri-Wizard Tourney makes little sense when you think about it, and I thought it brinked close on making the whole wizarding world make little sense. Previous books made Hogwarts seem like it was one of a kind in the world. This muddles things, kind of in an interesting way, but I don't think JK has played her full hand on explaining the inner details and structure of the wizarding world and school system. I will wait until she brings out her encyclopedia. Without getting into details on this one, earlier books make Hogwarts seem like one of a kind (no other schools are ever mentioned--you'd think they'd come up), but in GoF we get the Tri-Wizard tourney that turns our conceptions of the world on their ear. Why weren't these other schools ever mentioned.
I also think the actual Tournament was wonky, too, but I think that is getting into subjective territory. I feel that objectively, Rowling did a pretty haphazard job with constructing Hogwarts, and possibly with the wizarding world at large. It turned out alright though, so no shame.