The Ryukyu shrink from the bearers of European enlightenment as from the plague. They must be made to need it, however, since, as a European, Goncharov considers it a natural and universal stage of human civilization. He relegates considerable evidence of Ryukyuan material prosperity and moral advancement—both of which cast in unflattering relief quite big sections of nineteenthcentury Europe— to the mundane, material end of the spectrum. Its opposite end is a “spiritual” realm, into which the Ryukyuans have apparently not strayed, but which they must be helped along to reach, for the sake of the proper unfolding of Eurocentric conceptions of human history. And so, even a paradise may use improvement after all.

提醒一下
cast sb into prison
倒装一下就是那个句子

应该是浮雕的比喻义。比如朗文的6，bring / throw sth into relief，用的应该就是浮雕的比喻义。bring和throw应该是常见的搭配，cast较为少见，所以词典里没有收录，但用法应该是一样的。
5. DECORATION 装饰, C,Ua way of decorating wood, stone etc with a shape or figure that is raised above the surface, or the decoration itself浮雕; 浮雕品;
⇒bas-relief:
in relief•figures carved in relief浮雕人
6. bring / throw sth into relief also stand out in relief to make something very noticeable, or to be very noticeable（使某事物）格外引人注目:
sharp / stark relief•The tree stood out in stark relief against the snow.树在白雪的映衬下显得格外醒目。•The article throws into sharp relief the differences between the two theories.文章使两种理论的区别更加明显。

这个句子中，“cast in unflattering relief”实际上是在说一种对比的效果，但它并不是在赞美或正面地展示某物，而是以一种不太光彩的方式突出了另一方的不足。具体来说，这里指的是琉球（Ryukyu）的物质繁荣和道德进步与19世纪欧洲的情况形成了鲜明对比，而这种对比使得欧洲的某些方面看起来不那么出色或者有些落后。
简单来说，这句话的意思是：琉球的物质繁荣和道德进步被用来作为参照，突显出19世纪欧洲在某些方面的不足。这种对比并不是为了赞扬琉球，而是为了强调欧洲在这些领域的相对滞后。

relief在这里是对比鲜明的意思

字不离词
词不离句
句不离章
作者在批判公差洛夫的观点。所以文章在两种观点之间切换。一不小心，就掉坑里了。
显然被批判的是公差洛夫的欧洲人优越感。

正常语序是Ryukyuan material prosperity and moral advancement cast big sections of nineteenth-century Europe in unflattering relief. 这里的relief是从【抬升】引申出的【浮雕】进而延伸到【使XXX凸显】，加上了unflattering，就成了“使XXX相形见绌”。

通常人家当面赞美你，你可以说 I am flattered. 意思是，我只有7分，你把我说成9分。
所以flattering 意思是，描述比真实更好，文胜质也。unflattering 是，描述没有真实那么好。质胜文也。
in unflattering relief, 意思是 欧洲19世纪在物质和道德精神层面都有巨大【难以溢美】的进展。明朝欧洲人到中国来还惊艳于中国的进步。当时欧洲城市充满着泥泞肮脏的街道。
此部分和琉球无关，而是谈到欧洲历史发展。所以用破折号插入。