Why doesn't Rudong develop south?

For example, the economic development of southeast China is close to saturation. According to Rudong's data, Rudong does not develop to the south because the economic development in the southeast is close to saturation. Rudong County is a county under the jurisdiction of Nantong City, Jiangsu Province, which is located in the southeast of Jiangsu Province and the north wing of the Yangtze River Delta. The county is connected to Tongzhou District in the south, Rugao City in the west, Hai 'an City in the northwest and the Yellow Sea in the east and north. The land area is 2 122 square kilometers and the sea area under its jurisdiction is 4965 square kilometers.