Just because an author insists he didn't write something as an allegory doesn't mean we can't read it as one. IMHO
JRRT was reworking the stories of Western culture, weaving a whole lot of stuff together to tell a mythic tale. He was (as we all are) approaching the raw material from his particular point of view as an Englishman of the early 20th century,whose main preoccupation was linguistics. All that stuff (and a bunch more) inevitably colours his writing of the story, just as our "stuff" colours our reading - and appreciation - of it.
The maker of the film had to rework this material once again in his medium; it's a different piece of art and as such, is subject to all the changes that have taken place in the world in the time since the writing of the book. I think it's still a great story and a pretty good movie. Like the Star Wars movies (for me, at least) it will probably seem a lot better when I have been able to see it in the context of the entire trilogy. I have lived with Tolkien's images since the late 60's and didn't find the movie clashing with them as annoyingly as Ralph Bakshi's cartoon version did (what a mess that was).
I am reading the books yet again this year, after finishing the 4th Harry Potter book. Harry has quite grown on me, although I was a bit put off at first. Once I realized that Rowling was also reworking the mythical and legendary stuff, and once I saw that she had some craft to her, I was able to relax and stopped making pointless comparisons. Now I have something literary to look forward to. And something to look forward too in the movies, too. Life gets better and better.