Nearly every line here follows the same pattern: "What we..." followed by something bleak. Appearances are lies, ambitions are out of reach, and anything we do manage to get falls apart or turns to ruin. The senses go wrong too. Sight shows rot, smell shows decay, taste is metallic, and hearing brings only screaming. Touch gives us "nothing," which may be the saddest detail of all.
Two lines twist the pattern in a strange way: "What we take is happiness" and "What we drink is suffering." Happiness seems to be something grabbed, not earned, while suffering is swallowed like a drink we can't refuse.
The relentless repetition builds a heavy, numb mood, like someone sinking into despair. Then the poem turns to its question, "What are we?", and repeats it as if the speaker is stuck. The final line, "Who are you?", turns the question outward and puts it to the reader. The speaker seems to feel empty and disillusioned, and wants us to share that unease.