I believe the reason some people do not like LOTR is because they do not understand it. Generally, people don't like what they can't understand (take science and the paranormal as an example if you like).
Tolkien's works are deep and full of meanings, which makes them the length they are. That is another thing that will put someone off reading the books. The time that it would take them to complete it, and the time it would take for it to sink in (two very different things when you read such a book).
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