They couldn't do that easily, though, as then they would either have had--in accord with the book--to have shown Denethor to have the strength of will to resist Sauron's influence, yielding rather to what he saw rather than Sauron's corruption; or they would have had to explain why Sauron didn't just flip him and overturn Minas Tirith with a bloodless coup.

The movie-Denethor had his apparent greatness severely curtailed compared to book-Denethor.

I think the films are decent cinema, but the cinematic aspects would not have suffered and the story would have been better (and more faithful) if they'd followed the books more closely in those areas.

I do agree that certain things--like ditching Bombadil, like replacing the otherwise-plot-irrelevant Glorfindel with Arwen--were good calls. But a lot of the changes were just in the service of a different and, I'd argue, inferior vision.

Amazon could have done considerably better to persuade people that they have a sufficiently Tolkienesque vision.