This is a poem mourning the monuments of the Six Dynasties. Why do poets say "Taichengliu" and "heartless"

"The most heartless is the willow in Taicheng", and the most heartless is the willow in Taicheng. It doesn't care about the rise and fall of personnel and the replacement of dynasties, nor does it care about the sadness and disappointment brought by the poet's mourning for historical sites.

With Liu Yang's "ruthlessness", this poem asks the poet to face up to the pain of the changes of the times, and metaphorically hurts the present in the historical emotion. Ruthlessness is the most ruthless willow in Taicheng. On the surface, it accused Liu Yang of being heartless. In fact, facing the long river of history, what can Liu Yang do and what can poets do? Therefore, the poet should sigh: Why is the prosperity of the Six Dynasties gone forever?