Xi repeatedly emphasized this point for one fundamental reason: the legitimacy of the Communist Party in power.
In its early years as a nominally socialist country, China's political party was guided by Marxism. However, after the official establishment of the PRC, a frenzy of individual worship took hold in China. This event led to a change in the guiding ideology of the Chinese Communist Party from Marxism-Leninism to Mao Zedong Thought. Despite the end of the Cultural Revolution, China's leaders were still keen to summarize their governing philosophy as "XXX's Thought" and write it into the Communist Party's constitution. As a result of this shift, China was not in fact a socialist country and the party's philosophy was far from Marxist-Leninist, but most Chinese, they still believed that China is a socialist country, so the Communist Party did not need to worry about its legitimacy being challenged before the Xi era. During Xi's reign, with the rapid development of the Internet in China, more and more facts that had been deliberately buried by the Communist Party were revealed, and this was the first time that the Communist Party was challenged about the legitimacy of its rule. Because of this, Xi will frantically tighten internet blocking and speech control. In this regard, he has been very successful, and I personally believe that this is his greatest achievement in office. However, since the covid happened, along with the global economic downturn, more and more problems have emerged in China under Xi's leadership, for example, China's covid test was paid for by public health insurance funds, and in three years, the covid test cost public health insurance funds 1.7 trillion RMB. This money was taken by Xi-led interest groups. Speaking of this, we have to mention Xi's fight against political opponents in the name of anti-corruption when he first became president. Nominally he was fighting corruption, but in reality, he was bringing together scattered interest groups from all over China for his use.
The situation in China is not good now, the economy is on the verge of collapse the main reason (for example, the complete collapse of the Chinese real estate market), and Pelosi's visit to Taiwan has exacerbated internal conflicts, for the Communist Party, the recovery of Taiwan is a huge dream they have prepared for the Chinese. Resistance and rhetoric began to emerge everywhere. For these reasons, the legitimacy of the Communist Party is once again being challenged, and Xi has therefore repeatedly emphasized in this year's conference the "people-centered" basis on which the party was founded, in order to give the people confidence and to keep their trust in the Communist Party and in his leadership.
Here is my personal opinion:
Many people think Xi is a loser because China under his leadership has really become more and more conservative and many of his policies are ridiculous (e.g. radical environmental policies). I don't think so, Xi was ambitious because before he came to power he appeared to be a very controlled and weak man, and this impression led directly to his selection by Jiang Zemin as his successor. However, due to his education level (his real education was only elementary school dropout), he could not contribute much to economic construction, but he was convinced that his policies were effective (Chinese government departments have a habit of reporting false data), and probably in his heart he really thought he was doing it for the good of the people. This may also be the reason why he came up with this slogan.
Sorry for being a bit off-topic, but I hope you can learn more from my answer.