It is difficult to the point of impossibility for the average reader under the age of forty to imagine a time when high-quality arts criticism could be found in most big-city newspapers.

【重点词汇】arts criticism 艺术评论

【结构分析】句子主干：It is difficult for the average readers to imagine a time.主干为It形式主语句型：It is +形容词+for sb to do sth

修饰成分to the point of impossibility意为达到不可能的程度，修饰difficult，可以理解为“非常困难”;介词短语under the age of forty作定语修饰reader;when high-quality arts criticism could be found in most big-city newspapers为when引导的定语从句修饰time，由于此处的定语从句较长，可采取后置法进行翻译。

【参考译文】对于年龄低于40岁的普通读者而言，他们无法想象一个时代，那时大多数大城市的报纸上都刊登了高质量的文艺评论。