Leaving the trolls like Beidou aside, China has done well with its model, and so has Singapore - I'm not denying that. The path of autocracy however could easily swing a country in its stage of development into a North Korea like system while democracy is a system that has inherently less risker, albeit lesser return. Each country needs to find its balance in this aspect.
India is culturally, religiously, ethnically, linguistically diverse. We cannot have one solution that works for all which is where democracy and interplay of power between center and state plays a role. Look at what happened in Pakistan when they tried to impose Urdu over Bengal or in Sri Lanka when they tried to impose Sinhalese over Tamil or even in India with Hindi vs Tamil. That simply does not work for the republic.
India has been really on the growth track only in the last 24 years after liberalization and income per capita in that period has quadrupled averaging 6% a year. Is this super fast to the levels of China? no - but is this acceptable? Absolutely - we would be happy if we can maintain this 6-7% a year over the next 25 years while strengthening the foundational institutions of our democracy.
Democracy is also the reason why many talented politicians lose their ground. In a developing country, it's not possible to expect people to make an intelligent judgement on who should be ruling the state. So the outcome is, having the most popular crooks being elected solely for the reason that they managed to influence the minds of working class. This is where it eliminates the potential of the country to address its problems properly. You can't expect many people to willingly sacrifice their comfort for the sake of greater good. So the chances are, any politician who's willing to drag the country forward gets rooted out from the system just because his actions inevitably causes discomfort for a short period of time.
Another issue is that, in any democratic nation -whether rich or poor, the leader doesn't have the ability to think beyond then next election. So many tend to take actions that could harm the country in return for securing the vote base. For instance, increasing salaries that otherwise, cannot be sustained. So again, long-term planning can't be expected in such an environment.
To avoid a country being turned into a heavily authoritarian state like North Korea, it is vital to straighten the institutions that does checks and balances in a professional manner, most importantly an independent judiciary. In many democratic developing countries, media is expected to replace the role of professional institutions which turns the entire political atmosphere into a meaningless competition. It is again, play an important role in combating corruption. Instead of expecting journalists, whose claims could be true or false, to provide complete coverage over corruption, a country should have institutions that deal with facts rather than opinions.
China is also a diverse country under the surface but they are more capable of settling their differences without igniting conflicts. Since you brought Singapore, it is also a diverse country that had to face many challenges. At the time of its independence it was full of racial tensions but it has managed to implement unique solutions that fit their requirement. In a fully democratic system, this would have never been possible. Simply for the reason that in such a system, its leaders may have to appeal to the majority to secure their vote base but in Singapore, leaders have taken some decisions that were, at the time, against the wishes of the majority. What's the result? A stable prosperous country. Therefore, just like Singapore, India should find its own solutions for its own problems rather than taking a foreign system and fully implementing it without considering how it will be played in the country.
IMO politics should be a professional area of work. At the same time. tt should be open to everyone given that a person has necessary skills and qualifications. Who should governs the country shouldn't depend on the opinion of the citizens. Just like how every random person in the country don't decide which doctor should treat a certain patient, politics should also be there for the professionals.