Life in a KMT-led China would have been considerably worse than in OTL's China. Yes, the Great Leap Forward and the Cultural Revolution were horrible humanitarian disasters, but the CCP did so many incredibly good things for the chinese people that the KMT couldn't and wouldn't have done.
To quote from "Impact of the Rural Reform on Financing - Rural Health Services in China" by
Mary Young (specialist in global health and child development at the World Bank):
"After the liberation, during the period from 1950 to 1980, the health status of the Chinese people has improved remarkably. Public health measures, combined with a reduction in malnutrition and improved water supplies and
sanitation, have reduced the infant mortality rate from 250 per 1000 live births in 1950 to less than 50 in 1980. Life expectancy increased from 35 in 1949 to almost 70 in 1980 (1). Indeed, the achievement of accessible primary
health care for virtually all people in a country with a per capita income as low as $290 (1980) is unique in the world (2)."
The massive increase in life expectancy and the rapid decline of infant mortality were a direct result of the CCP's "Patriotic Health Campaigns" (including the institutionalization of the famous barefoot doctors, large-scale midwifery training, campaigns against malnutrition and the implementation of the iron rice bowl, massive improvement of the water supply, and immunization promotion). These campaigns would not have been possible without the CCP's land reforms and anti-illiteracy efforts (which themselves would not have been possible without the jiǎntǐzì).
The "Patriotic Health Campaigns" safed the lives of dozens (if not hundreds) of millions of chinese people. Just think about it: Within 30 years, infant mortality decreased fivefold. When the CCP took power in 1949, the population of China was 542 million. When Mao died in 1976 the population had allmost doubled, reaching 930 million.
Per capita GDP (PPP) increased sixfold between 1950 and 1980, despite the fact that the population in the same timeframe doubled. With the exception of the Great Leap Forward, the CCP's economic pollicies were extremely successfull (which was the main reason why an incredibly overoptimistic campaign like the Great Leap Forward was attempted in the first place. The party suffered from the "dizzy with success" syndrome).
Now, a more competent CCP leadership could have definetly attained these archievements without the disasters of the Great Leap Forward and the Cultural Revolution. However the KMT couldn't.
After WW2 the ROC suffered from massive hyperinflation, uncontrollable organized crime, widespread destruction following WW2, rampant malnutrition and diseases, a massive inflow of american capital and goods that bankrupted chinese corporations, a huge wealth disparity, and heavy pollitical instability (both within and outside of the KMT). The future doesn't look too rosy for China had this state of affairs continued. It'd be a much poorer and less populous country (there wouldn't be a need for a "One Child Pollicy", because, as a result of increased infant mortality, there would be less people to begin with).
Overall it'd be comparable to India, yet more unstable and heavily dependent on the US economically (at least for the time beeing).