Here's why:
* Focus on personal emotions and thoughts: The poem explores Keats' anxieties about his mortality and his inability to fully express his artistic vision.
* Musicality and rhythm: Keats uses a variety of poetic devices, including rhyme, meter, and imagery, to create a musical and emotionally charged effect.
* First-person perspective: The poem is written from the speaker's (Keats') point of view, expressing his innermost feelings.
While it's a lyric poem, it also incorporates elements of elegy (a poem of mourning, often reflecting on death) and confessional poetry (poetry that reveals the poet's personal experiences and thoughts).