先来把这个句子后半句翻译一下：
yet on his deathbed he himself sought to prevent its publication on the grounds of (not being )sufficiently polished.
不过在他临终之前,他自己基于诗句没有被足够地润色过的原因,曾经想过停止这篇诗作的出版.
be polished 这个谓语,所对应的逻辑主语是the poem,而此处的逻辑主语是its publication,所以不能用这个not being polished.
这个地方可以改成这样的动名词：……on the grounds of (the poem's not being)……polished.