At the end of "The Fellowship of the Ring,"
I heard people walking out of the theatre grumbling about the non-ending.
They obviously had not read the book, so who cares what they think.
Ending the movie there made sense to everyone who matters.
The others deserve no consideration.

Breaking Harry's fourth year at the Ball scene could have worked. Maybe find a mini cliff-hanger in the Rita / Hagrid story.

Ending the fifth year just after the attack on Arthur could work, too. You could make a cliff-hanger about whether he survives or not.

We could sit here and toss out ideas 'till the cows come home. They're easy to do when you want to. When you care. The point is that these bozos should try. It's a great book and deserves a great movie. They are not making an honest effort. They know that they are churning out trash and they don't care.