Democracy is a model that is successfully replicated around the world. There are very few taker for chinese model (the maturity which you got through a painful process in which thousands died).
showing 1 or two exception and wondering why is it not the rule is missing the point.
The question can be flipped and said why not many countries replicated chinese model? why other communist countries could evolve to such model that cound have worked as alternative to democracy.
If you are generally in favour of authoritarian model, I guess statistics is quite clear. 1 brilliant china (since 70s) does not change it, nor did a brilliant soviet till 90s.
So why is it that China has by far the best economic performance in the developing world?
Take a look at any "developing democracy" around the world. In Africa, in the Middle East, even in your own neighborhood (South Asia), including your own country.
What you are doing is risky, and it shows. The standard throughout modern history is authoritarianism during the developing stage, and democracy during the developed stage. That's how it has always been done.
You guys are trying to go for a democracy first, before you are industrialized.
Even more, India is trying to skip the industrialization stage, and go straight for services.
Neither of those has been successful before for any major country. You're the one taking the very risky path, and so far it doesn't seem to be working for you. In terms of development indicators (life expectancy, maternal mortality ratio, etc), you are the 2nd worst in South Asia, behind countries like Bangladesh. Whereas China's indicators are almost the same as many already developed countries.
I think Democracy is a great system, but for developed countries. For developing countries it has an awful track record, and you can see that all around you.