The 'problem' with Tolkien (and it's not really a problem, but it *is* the thing we're discussing here) is that he didn't write LOTR to be a story. Or, at least, the story wasn't his primary motivation (or so I've been led to understand.) To him, the world--and especially the language--was the focus of the book. With that in mind, it probably didn't really matter to him whether LOTR was self-contained, or if people understood why the elves went to the Undying lands, or any of that sort of thing. These are plotting elements which had no specific relevance--he was writing a history of a world that never existed, not a story specifically meant to entertain.
Every 'problem' I have with Tolkien comes from this idea. I don't like that so many of the characters feel flat (everyone but the hobbit ring trio.) By 'flat,' I mean that they lacked internal, personal conflicts. In Tolkien's mind, however, these things not only weren't important--they had already been resolved. There was no need for Aragorn to brood over whether he should become king or not. I think Jackson correctly added some of these character conflicts when he made the movies. But, it wasn’t really a problem in the original--the thing is, you just can’t do everything. There isn’t enough space in a book format. One couldn’t have all of the Tolkien setting *and* all of the character drama, otherwise the book would be far too slow and the plot would suffer. Tolkien did what he did very well--better than anyone else ever has--but what he did is not currently what I want to teach my students.