I've read the hobbit but never the LOTR, but in the making of LOTR videos they point out (a few times I think) that Tolkein's writing style was highly unusual and extremely difficult to adapt to a screenplay. It's been awhile since I saw them but one comment they made was that Tolkein seemed to just keep the story elements flowing on and on almost like he was writing more of a historical account rather than a novel with a classic arc. What we got on film was the classic arc more or less, meaning they had to twist and bend the source material somehow. They basically thought that a faithful adaption would not have found wide audience appeal because Tolkien broke too many rules of writing novels.
I had read the LOTR several times, but it wasn't until I listened to it as an audiobook did it click for me just how much of the spoken dialog in the movies is pretty much word-for-word from the books. I get what you and others are saying about Tolkiens narrative style, but a lot of the dialog transitioned well to the big screen.
And it's mixed up with awfully bad Hollywood lines such as "Because I believe there is still Good in this world". Such a poor written next to Tolkien's.
I wonder though..