Several of Emily Dickinson's poems express a desire for personal connection but few of her poems speak to cultural or social connections. Because she spent most of her adult life avoiding physical contact with people, her poems, for the most part, are relentlessly personal, very connected to nature, but seldom concerned with establishing relationships with people or society as a whole.
We see, however, in a few of her poems an attempt to reach out beyond herself to individuals. In "If I can stop one Heart from breaking," she says
If I can stop one Heart from breaking/I shall not live in vain/If I can ease one Life the Aching/or cool one Pain. . .
This is one of a handful of poems in her entire canon in which Dickinson abandons her internal monologue and expresses concern for another person's pain. That is not to say that Dickinson is selfish, but her focus is usually on how she perceives nature and the world rather than on how the world effects another person. Because Dickinson suffered various illnesses during her life, I think she sensitive to other's sufferings, and this poem represents that drive to alleviate pain if she can.
In another poem, "Success is counted sweetest," she steps outside herself to describe how success and failure are perceived by those who fail, and the poem as a startlingly modern sensibility:
As he defeated--dying--/On whose forbidden ear/The distant strains of triumph/Burst agonized and clear!
The gist of the poem is that only those who are defeated--the failures--understand the sweetness of success, and she depicts a dying soldier on the field, listening to, and agonized by, the sounds of triumph that he will never experience. She has moved far outside her normal milieu to imagine such a scene with, I would argue, a very modern psychological insight of a dying, and totally conscious that he's dying, soldier.
Clearly, the majority of Dickinson's poetry expresses Dickinson's feelings about very private concerns--her relationship to nature, death and dying, illness--but there is evidence that her wide-ranging mind included universal human concerns.
I think that the statement operates under the assumption that the poetry of Dickinson presents an unsettling reality towards not belonging. I am not entirely sure that this is the case in her poetry. Powerful and unsettling images are present, but I don't see them as geared towards statements of not belonging. Infact, I think that a case can be made that there is an element of belonging, but on the terms of a position that embraces individualism. The desire for belonging flies in the face of the exclusion and the sense of independence that Dickinson seems to write about in such an intense manner. I don't see her as one yearning to be with others, but rather one who is free to examine "the circumference" of the world around her. When she writes in "I'm no one, who are you?" about belonging, it is done out of a position where she is able to fully articulate the desire to belong, only on terms where there has already been isolation. Dickinson asks the question of belonging to one who has been set aside, one who practices exclusion like she has. She is not opening this up to everyone and anyone. In this, Dickinson seeks to bring out something more powerful and more intense than any other experience of belonging. In "I Could Not Stop for Death," I think that this same idea of belonging is evident, but not one on conventional terms. Dickinson lauds the idea that her sense of "aloneness" is what enables this communication with death to occur. She recognizes that there is little way this can happen if she is bound to social conventions and if she reflects a "desire to belong" to it. In doing so, Dickinson has enabled herself to experience the aspects of belonging to something more transcendent that what social belonging might gear itself towards.