Obviously in the case of India and China there are other factors at play, but for me this is the elephant in the room
And is it still relevant to call the view that democracy _is_ the best form of government a "US-centric" idea, considering that the current US seems to not be concerned about (and sometimes even embrace) non-democratic powers, in-land and around the world? If anything, it sounds to me like over the past few years it became a US-centric idea that it's totally fine to not have democracy.
Not the person you responded to, but functional democracies require either an already-established functioning government, which can be efficiently perpetuated and controlled by elected leaders (think the United Kingdom); or a non-functioning government which can be effectively reformed and then perpetuated by elected leaders (think Taiwan). In both cases, functional democracies also require an electorate who can be brought to work towards a nation's major development goals.
There are countries for which none of these criteria can be reasonably met in the context of a democracy. One reason is if the electoral processes are so corrupt that no one competent is actually elected or, if they are accidentally competent, are too busy working towards their own and their cronies' ends to be effective leaders. The second is if there is underlying social strife which prevents people from working collaboratively towards nation building.
India fails in both counts: the corruption at all levels of government is nothing short of legendary, and the country as a whole is comprised of very diverse peoples who, historically, have had little reason to work together. Many African countries, rather tragically, are in the same boat: during the colonial era, "countries" were almost randomly assembled out of groups of people who historically had almost nothing in common. When the colonial powers left, they typically left nothing behind -- no knowledgeable and experienced administrators, no established universal education, and little or no social infrastructure. The people were then left to reinvent government from scratch, and the "country" more often than not was actually five separate nations of people who hated each other.
In sum, democracy is sort of an advanced form of government which, when introduced, really does need a somewhat coherent nation to already exist (in more cases) for it to work well. An autocratic or authoritarian government is usually the on-ramp, so long as it's reasonably functional and stable for long enough. Wherever democracy has persistently failed to take off, it's invariably a place in which the underlying foundation didn't exist to begin with.
On the US: while one could argue the US is becoming less democratic is some sense, Americans remain extremely wedded to the idea of democracy as an ideal or even a panacea. That’s what I mean when I called it a US-centric viewpoint, not all cultures share this idea or at least not to the same extreme extent.
For example I think a lot of Americans were genuinely surprised that “democracy” in Russia in the 1990s failed to produce good outcomes, whereas for others from different backgrounds this was less surprising
It’s the other way around. Countries that are well suited to democracy are the exception. You need to have a state, rule of law, etc., before you have democracy. Then you need generations of people socialized in the ideas that allow democratic societies to function. For example, in many places in the world, people are socialized to put their trust in leaders of extended kinship groups and clans rather than in neutral institutions. You can’t effectively have a democracy under those conditions.
On all those fronts, Americans were standing on the shoulders of giants. England has offices of civil government (like the Chancellor of the Exchequer) that have been in continuous operation for over 800 years. Many of the concepts of the constitution date back to the Magna Carta 800 years ago. There’s also the non-religious aspects of religion. Protestants were developing decentralized church governance 500 years ago. American democracy is the product of an 800-year long process where you’re slowly and incrementally molding the structure of society and the mindset of the people generation after generation.
Read De Tocqueville’s “Democracy in America,” where he describes the organic, bottom-up self governance that prevailed in America 150 years ago. That description bears no response to how an Indian or Iraqi village is governed. Those societies, like most, are structured and hierarchical. An individual owes obedience to the layers above (father, clan or tribe elders, all the way to the top). And those at the top have obligations flowing downward, to care and feed their subjects and maintain order. These societies are much better suited for benevolent dictatorships.