It’s the end of an era for American-owned social media sites in China—and for the former hope that such platforms would one day lead to open dialogue there. In 2009, China blocked access to Twitter and Facebook. Google left a year later after recognizing threats to its future there, not to mention attempts to censor and hack users’ accounts. Now, LinkedIn is shutting down its local iteration of the careers and networking site, which launched in 2014 after deciding to adhere to the Chinese government’s internet regulations. “While we’ve found success in helping Chinese members find jobs and economic opportunity,...