In 'The Love Song of J.Alfred Prufrock', 'people are spiritually empty' refers to what?
This refers to the depiction of modern urban society in the poem, which appears quite dull. Prufrock can be taken as representative of the modern urban dweller, pre-occupied with trivial things like clothes and hairstyles and making small talk over tea. There is nothing grand or noble or fulfilling about modern social life as depicted in this poem. At the same time, Prufrock does chafe against the restrictions of such a society.
The essential emptiness and sterility of this kind of life is further emphasised by the descriptions of the modern urban environment: the endless dreary streets, cheap restaurants and so on.