Tolkien was trying to make a new mythology, a new set of deeply resonant stories, for modern (especially English) culture, and he succeeded. He transformed fantasy, and founded the concept of high fantasy. His detailed legendarium (as his mythology is called) is a masterpiece of world-building, with deep symbolism and emotional complexity, a mythology with arguably more depth and room to explore than many ancient ones. Tolkien scholars work full-time to study it, and many more people draw from it explicitly and implicitly for their own art, in D&D and other more modern fantasy settings.