Thanks for adding my quote
I feel honoured. Just like to add that I personally have many close Pakistani friends and we openly talk about issues on life, culture, and politics all the time and would like to have similar conversations here.
I will try to explain it as concisely as i can.
Chinese whether they realise consciously or not look at arcs of history in the hundred year cycles and thousands of years arcs, we say long spans of time and reference history very casually in conversation. So we subconsciously understand history and what kept us alive and prosperous. Beyond the resilient family units, the core is a competent centralised government with its power base firmly inside China with its rulers deeply Chinese, although ethnically can be outsiders but must be 100% Chinese culturally. There were many instances in history, and that outside ethnicity was absorbed into China. Han ethnicity was not big because they just had a lot of kids, it was assimilation through culture. The difference between Chinese cultural assimilation and Islamic assimilation is geography. Islam and its followers seek to expand it boundlessly while Chinese culture will stop at its boundaries due to geography, will expand on that later.
Using the term "Middle Kingdom" is easier to explain than using "China" but they mean the same thing.
Formation of 3 key Middle Kingdom characteristics:
1. Centrality of civilisation (The view of exceptionalism)
2. Absorbing of Periphery and Invaders
3. Middle Kingdom governance
At the core of Chinese culture is family and lineage. From there we get the history of the Chinese civilization. Recent genetic testing showed 60% of Chinese people derive from 3 ancestors ranging 4000-6000 years ago possibly proving the Shennong (God Farmer), Huang Di (Yellow Emperor), and Yan Di (Flame Emperor) mythology.
https://en.wikipedia.org/wiki/Shennong
https://en.wikipedia.org/wiki/Yellow_Emperor
https://en.wikipedia.org/wiki/Yan_Emperor
https://en.wikipedia.org/wiki/Yan_Huang_Zisun
If i had a simple answer why China cannot be or difficult to be Islamic and or Non-Chinese religion and that is geography.
When the middle kingdom was fragmented during "Spring and Autumn Period" nearly all of the action took place in the central plains of China. It was basically a bloody multi-century long war for unification. Eventually unifying under the Qin Kingdom which previously was viewed as a non-civilized kingdom, even the Chu was viewed as non-civilized kingdom before, then accepted into the civilized club effectively being absorbed into the Middle Kingdom concept. The core of China (central plains) is enclosed by the ocean and mountains without any major civilizations anywhere nearby, at that time Korea and Japan didn't have many people and were tribal. This formed the idea of the outsider and Middle Kingdom exceptionalism, there were no other civilisation nearby thus forming the thinking that the Middle Kingdom center is civilisation and anything outside is barbarian. The Middle Kingdom views everyone outside as others and doesn't put them to the same standard as the Middle Kingdom, they wont expect them to have the same customs or require it.
The map can be misleading, in fact at some points there were hundreds of tiny kingdoms.
Europe also had the concept of the civilized world and barbarian world but they have a hard time unifying and its due to the mountain range in the center of Europe and river systems that divide the continent into shapes that look like modern national boundaries. Thus their natural state is division into seperate entities. Simply Europe is a Doughnut with a hole in the center and China is a ball.
China on the other hand has two major rivers that go through the central plains from West to East (Yellow river and Yangtze) which created the fertile plain but also flooded immense areas and killed many. Most of China's large natural disasters were floods from the rivers. The struggle throughout Chinese history was taming the rivers and making them useful for life but one small isolated tribe cannot do much thus a large and coordinated centralised bureaucracy is needed creating the Middle Kingdom governance. When that central power collapsed, the northern plains will almost instantly go into a state of war if fragmented and will quickly retake the rest of the country to reunify the Middle Kingdom.
Muslims pray facing the Kaaba in Mecca, this act of pray serves an as safe for information and is maintained through habit 5 times a day. It encode the message that the centre of your religion, your spirituality and eventually your loyalty is in mecca not the Middle Kingdom, for a smaller nation that is fine. But for China is destabilising and eventually if unified will become unislamic again. Refer to history, Moscow was the center of the Communist movement and thought that they could lead all socialist countries to communism, but soon they found out that China would not comply with their policies. Its because China has very different priorities, thus in 1962 relations soured. Noticed how as time progress the natural state of China begins to show, beyond the foreign ideologies China is transforming from communist ideals to "socialism with chinese characteristics", which is very far off from the original and was called capitalist traitors by USSR. Simply because China is so hard to govern that it requires it to take a very different path from the rest of the world, no other civilization went through similar journies and cant really help in governing China. The same can be said of Catholicism with the Vatican, probably worse considering they have a leading political figure who is also the legal king (or emperor). When the Mongols ruled China they were not loyal to the land, they always thought "if we don't succeed in holding China we can always go back to the stepps". Meanwhile the Manchus were much more successful because the few hundred years leading up to the Qing dynasty they were studying confusion philosophy and Chinese texts effectivly sino-fying themselves willingly. When they ruled Middle Kingdom they moved their entire forces into the central plains and eventually assimilating. Islamic texts doesn't offer the governance necessary for the Middle Kingdom's environment.
Because China is so hard to govern, all ideological governments eventually collapse or become practical. If pork was banned (pre globalization) in China many people would have starved to death as pork is one of the cheapest sources of protein and can be raised in confined spaces). China doesn't have the vast expances of Arabia to grow herds of lamb for everyone. Many of Islam's practices are cultural offshoots of Arabian culture, thus strict adherence to the Quran would be and unhealthy imposing of a culture that has not formed in the Middle Kingdom environment.
There is a concept in China called "入乡随俗" which translates to "When in Rome do as the Romans do". The concept comes from the understanding of cultural formation. Culture is a mere manifestation human expression within a defined environment. Understanding that in a controlled environment humans are very similar, if placed in a certain environment that person should best adopt its local customs as those customs developed and survived for very good reasons, surviving the test of time.