Why is China's understanding of the Western Zhou Dynasty music a Goldbach conjecture?

In ancient times, many researchers thought Xizhou Qu was extremely difficult to understand, and even called it "Goldbach conjecture" in the literary research of the Southern Dynasties (see Chen Zhiming's Poem Appreciation Collection of the Han, Wei and Six Dynasties). It is believed that the main difficulty lies in the fact that the poetry of the whole poem is difficult to be smoothly explained throughout the whole article. It is because "the time, place, characters and plots involved in the poem are all dark and unclear, and it is difficult to get a consistent explanation." Therefore, how to correctly understand the content of this poem has long been a controversial issue in academic circles, and there is no unified view so far.