Fed up with work stress, Guo Jianlong quit a newspaper job in Beijing and moved to China’s mountain southwest to “lie flat.” Guo joined a small but visible handful of Chinese urban professionals who are rattling the ruling Communist Party by rejecting grueling careers for a “low-desire life.” That is clashing with the party’s message of success and consumerism as its celebrates the 100th anniversary of its founding. Guo, 44, became a freelance writer in Dali, a town in Yunnan province known for its traditional architecture and picturesque scenery. He married a woman he met there. “Work was OK, but...