Unnecessary and even detrimental changes from the book

Rating: 1/10 (12 January 2020)

I understand when you need to squeeze a book into a 2hr film, you have to change things, such as trimming details and simplifying the plot. But there is absolutely no reason to make Dumbledore a babbling baboon. The Dumbledore in the film is easily excitable and frivolous and has no grasp on the situation whatsoever. I absolutely disagree with the treatment of him.
Also book 4 marks a significant change of tones in the entire series with its ending dark and foreboding. But the end of the film seems unseasonably cheerful. Someone just died and the next moment everyone hugged each other goodbyes with a huge smile on their face. Why? Why change it from the book when it is entirely unnecessary and even harmful to the flow of the whole story?
Worst film in the series.