Herbert Giles (1845-1935) was a Cambridge Professor and Sinologist who left us with the Wade-Giles phonic system for Chinese. This work is much too short for my liking, but at the same time contains a number of curiosities, along with perhaps a caution that his scholarship might be no more accurate than his phonic system.
Religions of Ancient China begins with a description of the oldest Chinese religion, which he asserts to be monotheistic with two separate names for God. One is an abstract one, 天, while the other refers to a more animate deity, 上帝. Gradually a large number of other spirits appeared, but the earliest Jesuit missionaries found these original terms to be so similar in concept to Christianity that they adapted them, although the Pope insisted on the variant, 天主, "Lord of Heaven", which confusingly matched another Chinese deity. Confucianism tried to manage the multiplication of deities, but then Confucius was deified and a mess ensued.
Taoism had its beginnings primarily as a philosophical endeavor in speculating about theological matters. But then Buddhism came along as a distinct religion, and we have this note:
"Each religion began early to borrow from the other. In the words of the philosopher Chu Hsi, of the twelfth century, 'Buddhism stole the best features of Taoism; Taoism stole the worst features of Buddhism. It is as though one took a jewel from the other, and the loser recouped the loss with a stone.'
From Buddhism the Taoists borrowed their whole scheme of temples, priests, nuns and ritual. They drew up liturgies to resemble the Buddhist Sutras and also prayers for the dead. They adopted the idea of a Trinity, consisting of Lao Tzu, P'an Ku, and the Ruler of the Universe; and they further appropriated the Buddhist Purgatory with all its frightful terrors and tortures after death."
Reading between the lines, Buddhism didn't have any significant philosophical theology until it encountered Taoism. All this just sets up a big red flag in my mind regarding how little I actually know about Buddhism and Taoism, but it certainly reaffirms my suspicion that modern Westernized Buddhism is even further from original Buddhism than I had thought. There is also a note that Chinese Buddhism would have been unrecognizable to Buddha. My problem is that I have zero confidence in westerners to properly teach this subject, while the original texts aren't accessible to me.