We spend a ton of time in "The Passing of the Year" looking at people and trying to guess what they might be thinking or feeling. Your kindergarten teacher probably always told you not to judge a book by its cover. Still, that's exactly what we're doing here, right? Analyzing appearances, the way people look, is a totally central part of how this poem works.
The presence of a crowd of silent, staring, mysterious figures in this poem creates a feeling of deep isolation and loneliness that never quite goes away.
While we see a number of people in this poem, the dream-like, imaginary feeling makes it impossible to really know anything about them. This is a poem filled with illusions and phantoms, not breathing, living people.