Wandering through a few short lines, this poem makes one quiet, blunt claim: sometimes the world would be better off if it simply went quiet. The speaker doesn't say silence is peaceful or pretty. Instead, silence has a job to do. It holds up a mirror and shows us "what monsters we've become."
The speaker sounds tired and disappointed, maybe even a little angry, but there's no shouting here. The poem is soft-spoken, and that fits its message. Because it's so short and plain, the last word, "become," lands hard. It suggests we weren't always like this, and that we've drifted into cruelty without noticing.
The mood is somber and reflective. The poem doesn't name any specific wrongdoing, so we're left to fill in what the "monsters" might be. That openness makes it feel personal. When the noise stops, the poem implies, we may not like what we hear in ourselves.