Why is Lu You's poetic style close to Du Fu's gloomy and sad side?

However, such an era of internal troubles and foreign invasion is no longer the era of Li Bai's prosperous Tang Dynasty, and the dreamland in his dream will eventually disappear. The harsh realistic environment has caused an unavoidable burden on the poet's mind, so Lu You's poetic style has a gloomy and sad side close to Du Fu's, and his history is known as "the history of poetry". Lu You's unique poetic style combines Li Bai's elegance and Du Fu's depression and frustration. Lu's poems, though not as magnificent and unpredictable as Li and Du, are simple and fluent in language and well organized, even in the Seven Dynasties. Lu You is good at seven-character poetry, and he has made great achievements in seven ancient poems, seven rhythms and seven unique poems. Seven of them are especially famous for their neat antithesis, and Liu Kezhuang even said that "the good antithesis of the ancients was all used up". The antithesis of Lu's poems can often be neat but not exquisite, novel but not carved, and also shows the tendency of approachability. Seven verses lead the pen to flow, and the feeling is profound and eternal.