The title "Hubris" is an ironic one. The tone of the speaker reveals that this is so. Hubris means overbearing pride or arrogance. Arrogance means to have a feeling of self-importance and superiority over others. The poetic speaker's tone conveys the feeling or attitude of the speaker toward the subject of the poem, who is, in this poem, "The man in the next office."
The speaker’s tone reveals two important things at the start. The first is that the speaker does not take herself seriously; she expresses herself with self-irony as is shown when she says of herself:
while I shamelessly covet
his gray baseball jacket.
The second is that the speaker thinks very highly of "The man in the next office." She describes him as cultured, intellectual and of a dignified inner character through the simple phrase "he quotes Whitman" as they wait for the elevator.
The conclusion is that Karr wrote this poem as a tribute to "The man in the next office" and that the theme pointed to by the ironic title is not arrogance but rather humility as she diminishes her mundane feats ("to take the stairs ... two at a pop.") and elevates his stature in the face of his great feats:
he waves me on--
he says with cheer.
Maybe he doesn't mean
to be a figure of courage
with his cane and his corkscrew knee,
this smart man who can't reach
some sinks. ....