Broadly judged, the good outweighs by far the evil of the change.

broadly judged 为评注性状语，即说话人对句子的注释。

= It is broadly judged that the good outweighs by far the evil of the change.

由于后面句子的内容是判断（judge）的宾语从句。即句子与判断是被动关系，所以要用过去分词。

翻译：这种变化利远大于弊，这是总体判断。