I think this depends on the context ,how you measure development is highly relative.
For example, if you take into consideration the GNP of a nation, China is only behind the U.S. since 2009.
However if you go by GDP per capita nominal values, China is lurking at 83 according to the list given by IMF.
So what exactly is the indicator for the Development?
1) One of them could be unequal distribution of wealth, i.e the Gini co-efficient, which measures income inequalities is very high for China.
Edit 1 : Ideally the developed countries should have low Gini co-efficient. (barring the Anglo-Saxon countries)
Edit 2: Having said the above line, it might sound contradicting but we cannot compare the Gini co-efficients of two different countries, as the term is very relative. If in America, a person with least income owns a car and able to rent a decent house, but a person with least income in India and China have nothing.
2) ICOR (incremental capital output ration) could be another parameter on which we can make some guess as to why even after being such a big economy, China isn’t into the list of developed nations.
ICOR of China is very high, higher ICOR refers to the lower productivity of the capital.
3) Human Development Index: China stands at a distant 87th place according to recent reports which is definitely not the characteristic of developed nation.
4) Also the absence of democracy and human rights in China, could be attributed one of the factors for not calling she a Developed country.
While many tend to use the quotation “India is rich but Indians are poor”, it is apt for China too, “Chinese are poor, but China is rich.” For the fact that there are a few billionaires sitting at the top.