I've never read the poem, but I am quite certain that if it were theologically sound there would be be a firestorm of criticism and calumny surrounding it.
There is good reason to believe the story that Pope Pius XII verbally authorized its publication. Three supposedly highly credible people swore in writing that they were present when the pontiff made this declaration. From what I've been able to learn about the history of the index incident, the reason it was placed on the index was because it was published without an imprimatur, and not because it contained anything objectionable. The lack of an imprimatur was due to the publisher thinking it didn't need one since it already had the approval of the pope. The index was abolished shortly afterwards, before the matter could be sorted out.
I wouldn't be in too much of a hurry to believe accusations about scandalous content from unverifiable sources.