It has nothing at all to do with being a "developing country". There are plenty of "developing countries" that may (some) or may not (others) be progressing as well as China economically, but have already established political systems that are NOT dictatorships and where what freedoms and rights they have are foundational and not mere privileges that dictators agreed to give, for now.
But really, when you think about it, any degree of religious and political freedom in any country is fragile. Even in the U.S., the bastion of freedom, we see threats to our personal freedoms from the government albeit they are quite small at the moment.
Please, please go live and raise your children in a dictatorship. Maybe by the time they are ready for high school you will see the need to restore their lives to freedom. IF our freedoms are fragile, it is by our own doing that they have become so and yet we still possess the rights and the means to make them less so. In China, under the dictators "rights" are fragile by design, by intent and there is/has been zero progress in undoing that fragility or the intent for which they are fragile - giving up the dictatorship.
I disagree with you when you say that Chinese people understand that "there has been no real advance of real freedoms in China." Most Chinese people that I know do recognize the important changes in China to the degree that many of them think that everything here is just terrific now.
Shopping malls, new schools, new industries, cars, new homes, new amusements, travel DO NOT FREEDOM MAKE. "Changes" yes. Freedoms, NO.
Of course, I do not agree with that. As many have mentioned, China still has a totalitarian government that does suspend the freedoms that they claim to bestow upon the people quite frequently. China does have a long way to go but compared to 30 years ago, Chinese people feel a lot freer than now.
I disagree, and maybe that's because I know too many Chinese who seek real freedom for their country. Do the Chinese feel "better off" now, and more so than ever before? Yes, definitely. But "better off" is not freer.
The Chinese do not have a cultural tradition of Democratic Republicanism. Why should we expect them to be in accordance with your pipe dream (and that of other Freepers) of an American-style Constitutional government?