The average lifespan of the Chinese at the start of the revolution was 33 years of age, that's how horrible things were under the British, Americans and other western imperialists exploiting the country. It went up DURING the revolution, a time of civil war between the communists and the ROC combined with a literally genocidal fascist invasion by the Japanese.
Conditions were so bad that the communists still made people's lives better during those horrendous circumstances. By the time the new country was founded it had risen to 45 years, and by the time Mao died in 1976 it had risen to 62 years of age.
Were things just peachy during this time? No. Did they consistently improve the lives of the people? Yes. Were things significantly worse beforehand? 100%.
The maoist uprising against the landlords was the largest and most comprehensive proletarian revolution in history, and led to almost totally-equal redistribution of land among the peasantry.