“Hollywood doesn't understand books.”
No. Books and movies are two completely different mediums. It is not possible to condense a novel into a screenplay of 90-120 pages and retain every little detail.
Adding to that, novels tell and movies show. It is taboo to rely on voice over or blatant exposition to express what the characters are thinking and feeling in film. Film is a much more subtle medium in that sense. You will always have a stronger feel for characters in a novel because you know everything they think and feel. In a film you have subtext, tone and composition to name a few that have to be interpreted.
Film doesn’t have time to linger on every little detail. Film has to have clear themes and motifs that can’t be muddied with extraneous detail. The old rule of thumb: if a scene doesn’t progress the story it is unnecessary.
We’ve all read a book and seen the film afterwards and thought the same thing. “They left so much out.” Of course they did. Otherwise you’d be asleep in front of a seven hour movie.
Films are also products of their time. Sexual abuse and harassment is highly topical, ergo, they adapted a small aspect of the story and made physical abuse sexual abuse. Not a drastic change to the character or situation. It hardly ruins the intentions of the book.
Should they have explained horcruxes more in the final Harry Potter film? Maybe. Should they have cut out Hermione’s house elf rights movement subplot? Yes. Movies have to be very focused and streamlined. They have a limited time to invest you in story and character that a novel has the luxury of taking its time with.
