I think that the particular approach to poetry in the modern setting as represent in Auden's work owes much of its growth to Romantic thinkers like Byron. If Auden's work is taken to be a representation of the modern approach to poetry, it is a form that uses the subjective understanding of the world to better understand it. In this, the subjective becomes a means to grasp the universal. In this, Byron's belief is echoed and the Romantic thinkers are validated. Auden is able to turn much of the poem about his own sense of self to his own experiences and then broaden that to a larger configuration into which he and Byron are thrust.
Part of this need to absorb consciousness through the internal subjective realm is important because there are so many modern constructs that are confusing to the individual so that the only way to make sense of them is to assess them internally and to hope for some external condition. In this approach, Auden is able to use the Romantic stress on the individual sense of self to make sense of the economic condition and political state that surrounds him. While Byron might not have been dealing with such tremendous challenges, Auden is able to use subjectivism in order to both forge a link to the Romantic writer and attempt to construct some level of order in a world that lacks it. In the end, this is how Auden's "Letter to Lord Byron" takes an approach of integrating modern perspectives to poetic composition.