Why is "Leda and the Swan" considered a modern poem?

"Leda and the Swan," written in 1923, is considered a modern poem for several reasons.
First, it offers a fairly graphic description of a rape, such as the mention of Zeus's fingers pushing the "feathered glory from her loosening thighs" and "the shudder in the loins." A Victorian or Edwardian poem would almost certainly have referred to the rape more discreetly.
Second, the poem does not treat the sexual liaison as a seduction but directly faces that it was a brutal rape. This frankness reflects a modern consciousness that had been forced to come to terms with the brutality and violence of World War I and could no longer retreat into innocence.
Finally, just as in Yeats's cosmology, Leda's rape ushered in a cycle of violence that led to the fall of Troy. Yeats thought the world was entering another historical cycle of violence—an example of modern pessimism at odds with the optimism of the nineteenth century.