The negative urban images in the poem are juxtaposed with many very pleasant images. Some of these are the beautiful women and art in salons, and the mermaids frolicking in the sea at the end. This “feminine imagery” stays with me, rather than the negative ones of growing old, smoky streets, and lonely men. That is partly because of the rhythm and the sound of the words as they slip off the tongue, sublimating the ugliness inherent in some of the lines. See the full poem at:
https://allpoetry.com/The-Love-Song-Of-J.-Alfred-Prufrock
Shall I say, I have gone at dusk through narrow streets
And watched the smoke that rises from the pipes
Of lonely men in shirt-sleeves, leaning out of windows? …
I should have been a pair of ragged claws
Scuttling across the floors of silent seas.