What does the term courtier poet of middling talent mean

To understand this phrase you have to analyze it in pieces.

Courtier is a word to describe a person that goes to the court to present, in this case, poetry. The court was the place where the powerful people (kings, princes, queens, royal governors...) of society would go to have a different kind of reunions and presentations.

Middling is a word that was used as a synonym for standard, regular. Here it means that the poet is not particularly bright, not all that talented.

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serve the people! ,” smoothly translated by julia lovell, offers an initial sample of yan lianke’s writing to an english-speaking audience. a bluntly drawn, mildly erotic fable, it teases mao zedong by poking fun at a true believer who obeys the chairman’s precepts too literally. to a western sensibility, the broad strokes of yan lianke’s humor would seem to pose little risk of inciting rebellion, whether of the flesh or of the body politic. but then, part of the book’s attraction is that it doesn’t have a western sensibility. it lets the reader see — or rather, intuit — what jokes chinese officials don’t consider funny, and how very little it takes for a writer to be branded an incendiary in 21st-century china, more than three decades after the death of mao, a decade after the death of deng xiaoping and seven years since china entered the world trade organization, a move that would seem to signal a willingness (however wary) to mingle with the rest of the world.