No, sir or madam, China is not a failed socialist experiment. After all, not only does the People's Republic of China still exist, but as you allude to above, the Chinese Revolution is nearing the elimination of poverty in China. It took an average life expectancy in 1949 of 36 years and increased to 77.30 years in 2022, an increase of 0.22% from 2020. In the U.S., average life expectancy fell from 77 years in 2019 to 76.1 in 2022.
China also has the world's second-largest GDP, while in 1949, China's economy was in shambles.
So, no, "socialism with Chinese characteristics" is anything but a failed system. It isn't something that works well for anti-communists, but it is working well for the majority of the Chinese people, and that's all that matters.
I should also say that although many former socialist states no longer exist, that is not to say they were failed socialist experiments. Like socialist revolutions in the Soviet Union and China, their correlatives in Cuba, the German Democratic Republic, the balance of the Soviet Block, Mongolia, Vietnam, Ghana, Senegal, Burkina Faso, etc., lifted hundreds of millions of human beings out of poverty. Those changes in socioeconomic relations also served to significantly reduce illiteracy, infant mortality, neo-natal death, unemployment, homelessness, and even racism and sexism.
And in some societies where communism no longer exists, communism's positive legacies live on. In the Czech Republic and other former "Eastern Bloc" countries, for example, women are still granted maternity leaves of up to three (3) years, for their present capitalist governments became convinced of the benefits to society such generous maternity benefits provide. Compare that to the U.S., where maternity leave is virtually nonexistent, and the social landscape suffers accordingly.
To be sure, a socialist revolution is not a one-off event. It is a dialectical process that unfolds throughout time and various other socialist revolutions. They didn't fail in that they enriched the lives of millions in their time and served as guideposts for future socialist revolutions.