Similarities and differences between middle Tang poetry and prosperous Tang poetry

Mid-Tang poetry is not as heroic and graceful as the prosperous Tang Dynasty. In the prosperous Tang dynasty, there was a kind of gorgeous atmosphere that could not be concealed. Compare two poems:

Qing ping Diao Wang chun

Clouds need clothes and flowers, although the country is divided, mountains and rivers last forever. Trees and grass turn green again in spring.

The spring breeze opened the threshold and showed its richness. Sad state, can not help but burst into tears, amazing birds, leaving sorrow and hate.

If it weren't for the people in Yushantou, after three months of war, a letter from home would be worth a ton of gold.

I will meet Yaotai under the moon. Twisting with melancholy, scratching my head and thinking, the more I scratch my white hair, I can hardly insert a hairpin.

The former is Li Bai and the latter is Lao Du. The former is Li Bai's colourful love song praising Yang Guifei written in Ren Hanlin's imperial edict. The latter is that Lao Du lamented the sadness of his home country in the Anshi Rebellion.