Cities are dynamic in much the same manner as axe's that have handles and axe heads replaced .. while growing larger and spawing smaller axes about them.

The "Great Fire of London" took out a large chunk of the city which allowed for a clean slate redesign and rebuild of a district - it didn't wipe out the entire city, modern London is vast compared to the original Londinium Fort.

The original quote, as given, was that most cities in the world were built on the implied total ruin of prior cities - I'd argue that relatively few cities (not most) were built on the smoking ruins of near total destruction (74 cities at least in Japan fit the bill, along with roughly that number in Europe) with most having a more organic growth based on a long series of partial rebuilding of districts in rotation.

Thank you for your advice - I did once work on digitising a few hundred years worth of city records some 40 years ago.