Granted, so much of poetry is about personal expression. Poets describing their feelings and reactions to the world around them in imagery and language will most naturally use that pronoun. Sometimes, however, it may begin to interfere; egotistically the poet can become so self centered that his reader/listener begins to feel left out. However impressive the use of language and the skillful use of poetic devices, the poetry loses its audience and thereby becomes redundant, another "blowing in the wind."
A skillful poet will often use a mask. Rather than lay his own persona open before the world, he will create an "other," someone or something he can hold at arm's length. Whether such a character is named or remains nameless doesn't matter. What does matter is the poet's stance: this needs to be said but don't pin it to me as a person. Another way he may do this is by using the second person, "you." Then it becomes necessary for the reader/hearer to decide if he is referencing "me" or "not me." Either way, the poem implies that the self of the poet is not the main thrust of the poem.
And then there is the impersonal "I" where the poet puts himself in the place of a group of voices that includes his own. He may use the imperial plural "we" but more often remains with the first person singular. We are asked to see him as representative, the voice of the voiceless expressing truths held in common. This is the ancient and honoured function of the poet. He is everyone of us, speaking for the tribe, the voice of his people.
A great responsibility, but a great honour.