It stops being inconsistent when you think that the show is set a few thousand years before The Lord of the Rings. The best way to show the passing of time, especially when a race of immortals is involved, is to make costumes, hairstyles and architecture look different.
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The "ethereal look" about Elves does not really come from Tolkien, but from the readers. Personally, when I was reading LotR, I never got that impression. Yes, the Elves were wiser than Men, but they also seemed simple people. Samwise outright says so when he's talking about Rivendell. Some Elves are like great Lords, and other are as playful as children. When Bilbo reads his poem, you don't get the impression that his mocking critic is flying two feet above the ground. Gildor advises Frodo and is very down to earth. That's why I'm not too fond of Jackson's depiction of the Elves. And when you read the Silmarillion, well, it's simply impossible to get that "ethereal look". They are quite a different people in the First and Second Ages. In these times, they are like young adults or mature adults in their forties, full of fire and ambition. In the Third Age, they are all like a bunch of elderly people preparing to die. The time for new projects is over, and they stagnate. The Elves produced nothing new in Middle Earth during the three thousand years that the Third Age lasted. That "old age" makes them look a little more spiritual.