I'm right there with you. I felt that Return of the King was absolutely the weakest link in the trilogy. My biggest points of contention was the opening sequence which Peter Jackson admitted didn't belong in that movie, but he liked it so much he stuck it in anyway. The Pelennor Fields battle. And the depiction of Denethor.

The scenes with the battle didn't just fail on an adaptation level, it was just bad filmmaking. There was no weight or power behind the battles. As a viewer, I was completely underwhelmed and totally lacking in investment. And it's always a bad sign when people start giggling during the middle of it because the green soapy army of the dead was just so laughable. Awful execution, awful CGI right there. The worst failure was probably how they handled the character of Denethor. At first I blamed the actor for the horribly cheesy over-the-top portrayal of a mad king. But I've been watching Fringe and the actor, John Noble is phenomenal! He can play vulnerable with such poignancy and subtlety and when he needs to be powerful and intimidating, he can do it with force and gravity. So now I place all the blame on the direction and the screenwriting. The film Denethor was in your face CURRRAAAAZZY without any meaning or depth behind it. Having him catch on fire and run run run all the way to the cliff is another example of the cheesiness that Peter Jackson can't resist at times. He was robbed of all the things that made Denethor an interesting character. The intelligence, the pride, his loss of hope, and his despair. If given the chances, I think John Noble could have put out a much more subtle and powerful performance because he does it all the time on Fringe.

It's always been interesting to me that when Peter Jackson nails it, he gets it so right. Like, there are tons of examples in the movies that are perfection and can't be improved upon if you tried. But then when he gets it wrong, he gets it SO wrong.