First, since it is hieroglyphics, the context is hieroglyphics, and China characters come down in one continuous line, it is not too difficult to interpret the characters. As for the pronunciation at that time, although it was difficult, there were still some living fossils left in ancient Chinese in China, such as Hakka dialect in Fujian and Cantonese in Guangdong. The pronunciation of some words at that time was also mentioned in ancient books. Although there was no pinyin in ancient China, people in China used syncopation to mark the pronunciation of words, specifically using two words. Coupled with the analysis of the pronunciation law of each language family, and even the parameters of the unearthed ancient skull (analyzing the pronunciation law of the ancient vocal organs), the pronunciation of ancient Chinese can only be determined through the interaction of multiple disciplines, without excluding errors, but most of them are still based and cannot be mistaken for guesses.
Besides Chinese, there are also ancient Egyptian and Mayan hieroglyphs in the world. Ancient Egyptian characters were deciphered because of the Rosetta Stone and Copts. Mayan characters can't be fully explained because there are too few preserved materials, even if there are Mayan descendants.
In addition, many pronunciations of ancient Chinese (Oracle Bone Inscriptions and Jinwen) were determined by some China scholars and linguists before and at the beginning of liberation, and the academic style of the older generation was still very strict. Dude, this view is a bit biased.