The speaker has spent weeks watching a partner and has decided that he does nothing on purpose. Things simply happen around him, or fail to happen. The proof is small and domestic: three chests of drawers still waiting to be assembled in the hallway.
He has a theory that people secretly enjoy putting furniture together, which is why Ikea works. The company hands the labour to the customer, and the customer feels rewarded. The speaker's dry, slightly mocking retelling suggests she doesn't buy it. The couple did not enjoy the work, and the invitation to "hit a new relationship milestone" by building furniture together sounds more like a sarcastic quote than a romantic plan.
The ending is flat and deadpan: the drawers are still in the hallway. The mood is wry and tired, with quiet frustration underneath the jokes. The unbuilt furniture stands in for a relationship where talk and theories replace action.