The speaker admits to a quiet kind of guilt. Absorbed in making art, they have gone silent and held back from other people, giving "little of myself." The title, "(In)attentive," captures the tension: being attentive to one's work can mean being inattentive to everyone else, and the parentheses make the two words sit awkwardly together.
The second stanza turns to an image. The moon at noon is a pale, faint shape in a bright daytime sky, out of place and easy to overlook. Calling it "a brother / to no one" suggests isolation, as if it belongs to no family and has no companion. The speaker seems to see themselves in it: present but barely noticed, and cut off from others by their own devotion to work.
The mood is reflective and a little wistful. There's no dramatic complaint, just a calm recognition of what concentration costs. The poem's brevity and spare lines echo the silence it describes.