I think you're taking the question in an entirely different direction, with little relation to the canon at all. Obviously, the canon is not decided by dreariness - and one's opinion of what is dreary can be quite different from someone else's. Many people hate Paradise Lost - I find it quite intriguing, especially in its portrayal of Satan. Many, *many* students find "Beowulf" boring, and yet Tolkien loved "Beowulf" and attacked this drearified perception of it in "Beowulf: The Monsters and the Critics."
I don't think that any sort of theoretical bent is required to get a book in the canon; in fact, until the seventeenth century, few writers have any sort of intended theoretical bend to their stories. The foundations of the canon - Homer, Virgil, and more recently, Shakespeare - weren't working with deconstructionism or formalism. "Uncle Tom's Cabin," a *terrible* novel, makes it into the American canon because it played such an important role in history at that time.
Personally, I am a developing college student with plans of being a medievalist, and I am currently struggling with whether I want to work to bring Tolkien (perhaps kicking and screaming) into the canon. T.A. Shippey has started the process, but we've yet to see how much it will catch on. I can say, however, that most of the medievalists I've met here at Harvard revere Tolkien - both his critical and fictional works.
Regardless of whether Tolkien's fictional works make it into the canon, his contributions to medieval studies - especially Beowulf and Anglo-Saxon folklore - have already made it into the critical canon. In fact, the first time you see J.R.R. Tolkien's name in the Norton Anthology, it will probably be in Seamus Heaney's introduction to his translation of "Beowulf."