They posted videos on social media of the time he promised that China would remain open to the outside world. They shared photos of him, standing in ankle-deep mud, visiting victims of a flood. They even noted the economic growth target for the first year of his premiership: 7.5 percent.

The death Friday of Li Keqiang, 68, prompted spontaneous mourning online. Mr. Li served as premier, China’s No. 2 official, for a decade until last March.

Among many Chinese, Mr. Li’s death produced a swell of nostalgia for what he represented: a time of greater economic possibility and openness to private business. The reaction was jarring and showed the dissatisfaction in China with the leadership of Xi Jinping, China’s hard-line leader who grabbed an unprecedented third term in office last year after maneuvering to have the longstanding limit of two terms abolished.

In post after post on social media, people praised Mr. Li more for what he stood for and said than for what he was able to accomplish under Mr. Xi, who drove economic policymaking during Mr. Li’s period in office.

Mr. Li was possibly the least powerful premier in the history of the People’s Republic of China. The grief over his passing reflected the public’s sense of loss for an era of reform and growth that has been abandoned, and their deep sense of powerlessness in the China of Mr. Xi, the most authoritarian leader since Mao Zedong.

A post that was widely circulated on several social media sites said that many Chinese people saw themselves in Mr. Li — people “who have struggled over the past decade but have gradually lost ground.”

The most widely shared posts are short videos of Mr. Li promising that China’s door to the outside world would remain open: “Just like the Yangtze River and the Yellow River can’t flow backward.” Some of the videos were deleted later or couldn’t be shared after China’s censorship impulse kicked in.

On the social media platform Weibo, many posts that expressed shock over the suddenness of his death were censored. So were comments that referred to him as “a good premier for the people” and “a great man.” The comments that were allowed mostly went along the line of “rest in peace.”

For many people in China, Mr. Li’s death unleashed pent-up frustration, anger and anxiety about what they see as Mr. Xi’s mishandling of the economy. Mr. Xi went after the private sector, undermining some of China’s most successful companies. He alienated some of China’s biggest trading partners and got closer to countries like Russia, while replacing reform-minded leaders with loyalists. Mr. Xi turned the government’s focus more on ideology than the economy.

For them, Mr. Li, who had degrees in law and economics, represented the pragmatic technocrats who led the country out of poverty in the 1990s and 2000s. They recited his opening remarks in his first news conference in 2013 after becoming the premier.

“We will be loyal to the constitution, faithful to the people, and take the people’s wishes as the direction of our governance,” Mr. Li had said.

In commenting on his death, people said they couldn’t believe that the national growth target then was 7.5 percent. China’s economy fell short of its 5.5 percent target in 2022 and many analysts believe will miss less ambitious goals this year.

They recited Mr. Li’s most famous quotes: “Power must not be arbitrary” and “It’s harder to touch interests than souls.”

Quite a few business owners and investors shared photos of themselves with Mr. Li, who was a champion for entrepreneurship and innovation, when he visited their companies. They reminisced about the government encouraging new products and new business models, calling those the golden days of the entrepreneurship. “He left us suddenly,” wrote an internet businessman surnamed Ding. “And he took the golden age with him.”

They posted photos of him visiting Wuhan in January 2020 when Covid rampaged the city. Mr. Xi didn’t visit until nearly two months later after the initial spread of the virus had been contained. They posted photos of Mr. Li visiting the victims of flooding and earthquakes. Mr. Xi is known for staying away from the scenes of disasters.

They also shared a set of photos of Mr. Li chatting amicably with other government leaders, contrasting those scenes with Mr. Xi’s bossy body language when appearing with his associates.

Some people expressed their gratitude for Mr. Li’s honesty when, at a news conference in 2020, he noted that China might be the world’s second biggest economy, but there were 600 million people with a monthly income of $150. It was viewed as poking a hole in Mr. Xi’s claim of beating poverty.

“There are no perfect people, and there are no perfect politicians,” wrote a former journalist who goes by Yan Xiaoyun. “People should not forget Premier Li’s courage to uncover the truth.”

The public’s response Friday was the most significant outpouring of emotion since the White Paper movement last November, when thousands of Chinese in multiple cities went into the streets to protest the country’s harsh “zero Covid” policies and many more people joined the outcry online.

Deaths of senior leaders are always sensitive occasions in Chinese politics. Some journalists and commentators speculated whether Mr. Li’s death might stir a protest like the one in 1989 after Hu Yaobang, the sidelined former head of the Chinese Communist Party, died of a sudden heart attack. Most people concluded it probably would not since Mr. Xi controls the internet tightly. People speculated that Mr. Li would probably not be accorded a high-profile funeral like the one Mr. Hu got.

In contrast to the outpouring of grief from the public, China’s official media initially downplayed Mr. Li’s death. A 100-word announcement was listed as the third or fourth top item news on all major news websites, behind Mr. Xi’s meeting with Gov. Gavin Newsom of California or Mr. Xi’s new book on civil affairs work.

That low-key treatment resonated with people online because it reflected what they saw as Mr. Xi’s humiliating and disdainful treatment of Mr. Li, even after his death.

“He lived in frustration and died in resentment,” a Chinese journalist told me. “But aren’t we all like that?”