人心不古的英文是「human hearts are not what they were in the old days」
ren xin bu gu
古:指古代的社会风尚。旧时指人心奸诈、刻薄,没有古人淳厚。
清·李汝珍《镜花缘》第五十五回:“奈近来人心不古,都尚奢华。”