I really think you are discounting posts by
@Michael and other Chinese-origin members here. One of those said something like 'If you start from the bottom, then you have to be very smart to even rise to the top. So at least smart people can rise'. And Michael's posts clearly imply there is a lot of consultative process in the 'communist' China.
Well, I don't know about you, but I myself have seen people promote beyond their means.
I am not discounting their post; it may work in China, and maybe that was the way, but the thing is, what is good for China may not be good for others; that's the same way as what is good for the US may not be good for others. Different systems have different rules and different customs here. As I said before, you can't copy and paste it wholesale 1 to 1.
You seem to place a lot of focus on 'one man' decision making in your posts which doesn't seem to apply to China. Had it been the case then the modern China--which started from the ruins in 1949--would look even worse the dumps like India and Pakistan which started around the same time. But current China is very different and better than those two 'democracies'.
I lived in China for 20 years before 2000; I studied in China, and I can tell you that things are not always as rosy as you might think of modern China as all shiny and bright, and there are no problems within; is this the case? I tend to think every country had their own problems.
On the other hand, "success" is a subjective discussion; think of it this way: can the US build new buildings and new cities to appease people? Sure, it's just money and resources; they can build whatever they want, but then why didn't they do it? Is it because of Political disadvantage? Or was it because of the will? Or was it simply because that was not necessary?
Look, the political system is not a single measurement; it's not just simply a one-word wonder. Is it a good one when everyone is "happy"? Is it a good one when everyone is "rich"? Is it a good one when everyone is "healthy"? It was never defined by one single parameter, because a community is a matrix of factors, and no system is perfect. I love some Australian Politics and hate some, same as I love some American Politics and hate some aspect of it; the fact of the matter is if it work for you, works for your community, that's a good system.
As for China, Xi is the supreme leader, so yes, all decisions he made are his alone. Again, he may ask people for advice, but this is not a group decision like we make them in Congress, where the president only has the power to Veto but not to table bills. Xi can nominate policy and execute it, that means it's his power, and he alone has that power, not his consultant, not the People Congress.