As Prefect of the CDF, Ratzinger became the go-to person for sex abuse cases.  You are 100% right about his responsibility for his (mis)handling of sex abuse cases. But Ratzinger had been Pope Benedict for about five minutes when he acted against Maciel.  That prompts me to wonder what Ratzinger had said to John Paul about the Maciel case.  One of two things had to have happened:
1.) Ratzinger reviewed the Maciel case with John Paul, and said (paraphrasing now), "Karol, you have to do something about this son of a b*tch."  To which John Paul said ... what? What reason could he have given for not doing anything? Or ...
2.) Ratzinger never had that conversation with the pope ... which would be unconscionable.
I think the victims of Maciel have a right to know what Ratzinger did, and what he tried to do, about Maciel. (I think some version of the first scenario is likely.)  I think the whole church has a right to know.  And I think Pope Francis should ask him.