LOTR is a somewhat logical example, as the book/s itself is only a part of a yuge LOTR expanded universe. The movie was able to capitalize on the collective, accumulated knowledge of that universe (Peter Jackson must be a MAJOR nerd) and became a masterpiece!
The book is good only if you become a fan and start reading up on elf languages, Silmarillion, etc. And that's like 25 books to cram. The movies exqueezed all that into just above 11 hrs. It became like a very condensed flavor. And much more enjoyable as entertainment.
However, the books have their own advantage, when you read you imagine, you "co-create" that universe with the author in your imagination.
Welp, butt, you do have a point!