Due to China biggest decline since 19th century, many Chinese diaspora have to/been forced to abandon their identity and culture. Many Chinese disregard their own culture because Chinese identity was not a thing to be proud of any more.
In ancient times, even before 19th century, China links to power, elegant culture, high quality products, sophisticated political system, etc.
The decline of Chinese was because we were ruled by Manchu at that time. Not because Manchurian were bad. But because they couldn't really unite with the majority Han population. And that weakness caused a lot of civil war. Like Taiping rebellion, etc. Which weakened Qing National Power as a whole. That's why they couldn't compete with the western power.
I don't think it's specific Han culture. China merged so many ethnic and culture, it's a mixed stuff, and different Han Chinese behaves very differently.
Chinese looks similar, outsider may think they have the same culture, but actually not the same at all.
The northerners and southerners are very different, and east and west are different too, although they call themselves Chinese.
Also, we lost early start in Ming dynasty. Because the Emperor stopped the ocean expedition to another countries. If Zheng He model expedition was not stopped, who know what happen to China now. The richest that they brought, the knowledge, information, and maybe expansion will make China the 19th century English.
Manchu conquer, good or bad is very controversial. I think the major reason can be trace back to Northern Song Dynasty which lost Sixteen Prefectures https://en.wikipedia.org/wiki/Sixteen_Prefectures
, or even earlier, when Chinese adopted Confucian culture, but gradually become doctrinairism.
The Confucian culture between Han dynasty and Song dynasty are completely different thing.
Also the lesson Song learnt from Tang dynasty, An Lushan Rebellion, which is change of political situation, eunuch's politics and local separate regime politics. https://en.wikipedia.org/wiki/An_Lushan_Rebellion
But Song goes to the other end, oppressed militarism, kind of castrate Song dynasty herself.
It's not hard to imagine, any successful theory/ideology must be able to resolve the current political problem, which is how to end Warring States period, and stabilize China.
So is Confucianism.
Confucianism was born in the bloody Warring States period, the philosophers back in Han dynasty not only remember the what the Confucian emphasized, which is order and harmony, but also has deep understanding of human nature, which is selfishness, arrogance, aggressiveness, greed, cold blood.