Here's why:
* Focus on Emotion and Personal Experience: The poem is deeply personal, reflecting Yeats's feelings about the passage of time, loss, and the beauty of nature. He expresses his own emotions about aging and the changing landscape of Coole Park.
* Musicality and Imagery: The poem is rich in imagery and uses language that is evocative and rhythmically pleasing. Yeats uses metaphors, similes, and vivid descriptions to create a sense of beauty and melancholy.
* Focus on the Speaker: The poem is primarily about the speaker's subjective experience and inner world, rather than a narrative or a story.
While "The Wild Swans at Coole" has elements of other poetic forms, its focus on emotion, musicality, and the speaker's perspective makes it a clear example of lyric poetry.