The Cheezy One said:
He created his own world. If you had to describe everything in your country, it would be a touch drawn out, wouldn't it?
If you think that it is too austere, go for The Hobbit. It is basically LotR lite.
But worldbuilding alone, one could argue, does not necessarily make a great novelist.
There are plenty of great writers who set their stories in their own neighborhoods, and there are many very creative minds and world builders who would never get a novel through any publisher because they do not understand how to tell a story.
Now, of course Tolkien is not an extreme case, but a good example to illustrate how worldbuilding and storytelling are not necessarily reliant on each other. I agree, the world he created is amazing and he himself has displayed more interest in building that world rather than telling a story within it. Unfortunately, there is neither a good market nor huge prestige in writing mere descriptions of worlds, so he had to embed it in a story.
And the story, again, well, is not the best thing ever written in Fantasy. Is it entertaining? Sure. Is it interesting? Yeah. Is it influential? No doubt. However, the story takes the back seat with the world riding shotgun. That is something one has to keep in mind. Tolkien was a brilliant world builder, but an average storyteller.