"In the twilight of autumn it sailed out of Mithlond, until the seas of the Bent World fell away beneath it, and the winds of the round sky troubled it no more, and borne upon the high airs above the mists of the world it passed into the Ancient West, and an end was come for the Eldar of story and of song."-Of the Rings of Power and the Third Age
To me this is one of the most powerful passages Tolkien ever wrote. Anything mystical has died in the world, and the world has become truly demystified and structuralizable via the natural sciences. Everything has been explained and no mystery remains. Myth as personified by the elves is gone forever. The fulfillment of the enlightenment dream.
-The Silmarillion, Of the Ruin of Beleriand and the Fall of Fingolfin