You might just have to travel into unloaded chunks to correctly generate the Ancient City, if you decide that you do not want to travel farther you can take mobs into the city and kill them next to the skulk catalyst and that will spread the skulk to to the rest of the city if you rinse and repeat .
You might just have to travel into unloaded chunks to correctly generate the Ancient City, if you decide that you do not want to travel farther you can take mobs into the city and kill them next to the skulk catalyst and that will spread the skulk to to the rest of the city if you rinse and repeat .