I am at work and didn’t have a lot of time to respond before, but some clarification is in order.
Confucianism is not a religion.
It is much more like philosophy, or an ethical system.
Ancestor worship is not really worship per se, and is bound up in local custom, which happens to be heavily influenced by Confucian principles. But if Confucius never existed they would still be honoring the ancestors in some fashion, just as we do in our own customary ways.
The major traditional religions of China are Daoism and Buddhism (and those are in advanced states of decline in mailand China), and the nation has a large minority of Muslims.
Chrstianity is growing fast, but alas not so fast with the Catholics and Orthodox. It is the Protestant churches which are growing rapidly.
In the people of all of these groups, Confucianism has an influence, because it is the customary way of relating to one another. It is more than anything else a cultural practice, not a religious one.