Not sure I know what you mean by the points in the Dubia answer, but I think there are a number of inadequacies in the Church's position.  The brother/sister solution reduces marital fidelity to intercourse.  You don't live with someone as a sibling in a marriage even if there is no sex.  The discussion of divorce assumes there is an innocent and a guilty party.  It's often not that simple.  JPII said there were too many annulments while Francis wants the process streamlined.  How can anyone accurately remember their thoughts about marriage from 20 or 30 years ago? Some have said that marriage preparation is so shoddy that few marriages are valid.  A marriage is declared to have been invalid, but the children aren't "bastards." Children have to go through the trauma of a divorce and then the added trauma of an annulment.  A new spouse, who may not be Catholic, must have their life turned upside down because the Catholic spouse must divorce or comply with the sibling rule.