I admit I know nothing about screenwriting or film-making, so it's entirely possible that I'm talking rubbish, but I think there are some basic bits of good advice that apply to all writing. One of these is not to switch genres in mid-plot without a very good reason.
In a film like Harry Potter and the Goblet of Fire surely there's enough to contend with in weaving together the threads of the various genres Rowling so skilfully plays with in her text - fantasy, coming of age, mystery, school story etc - without turning what should clearly be an action-adventure sequence into vaguely psychological blundering. The only explanation I can think of is that the over-blown dragon sequence used up so much of the special effects budget that they had to cut back on the maze. I found this particularly annoying as one of Rowling's greatest strengths is in giving abstract concepts solid form: think Dementors and Boggarts for depression and fear.
There are a few minor wrong notes - sadly Michael Gambon provides several - but what does work works so well that they're forgivable. The Death (she says, evasively, as if there's anyone left on the planet who doesn't know who dies) is handled sensitively, the teenage relationships are as excruciating as an unforgivable curse, evil personified is effectively creepy, and the overall tone of juxtaposed light and dark is just right.
I think I might have to go and see it again.