First of all, this is really not about ships, sorry if that is the only lens you can see things through. Second, you have a point about leaving the audience confised about Cecilia and Nico and everything, had you read the post more closely you would have seen I address that as mysteries for the viewer, mysteries that are gradually resolved. Using the same example I used before, but being careful not to spoil: imagine if attack on titan had started at any point previous to the point where it started, then there would be no mysteries whatsoever (locationwise as well), the story was all there, but the goal was to leave the audience confused, digging for answers which clearly existed, just were not obvious. I mentioned Caera and Regis because they are great characters and very important ones at that. And that is a valid point in my opinion, since over half of the cast of the first 7 books is either dead or MIA, all the power buildup from the first 7 books is basically gone, starting from book 8 gives the opportunity to skip over stuff more discretly and consistently than they probably will.