I think people these days aren't so accepting of the Japenese Royal Family's succession rules. I think many people feel uncomfortable that the Crown Prince and Crown Princess' child will not succeed to the throne simply because she is a girl. I guess people think Kiko should speak out in some way against the situation that would make her Empress and her son Emperor over the child of her brother in law.
Yes I believe you are right-and I do agree with that sentiment that Aiko should be the heir.
But when it comes to Kiko-lets be honest-this is a woman with very little control of her own life-if her in-laws go on a trip she has to go to the airport to watch the plane come and go and she has to carry her gloves a certain way (just two small examples) There is no way she could ever say anything publicly about the situation. Or any situation, ever. (except for maybe her chief cause-sign language).
These are the same rules that Masako tried to rebel against and in turn they made her life a living hell, but Kiko was (when she married in) younger and less worldly than Masako and she obeyed them.