I mean not every one of them are new.
Oda changed 1 or 2 editors since dressrosa right?
His editors adviced him during dressrosa to not put up much screen time and development for Robin. They convinced him to not do so.
Editors in OP aren't like in Naruto, where they made the entire begging to be as good as it is...Editors in OP are like:
O:Well, we have a lot of characters... But you know who's missing right?
E: Let's fucking go Oda-sensei , just give TAMA more panels, who cares about Robin, Brook, Jinbe, Franky,Carrot,Kin...
And to make it better, give Yamato 1-2 pages each chapter, even when the character does nothing, better this than give any other relevant character a page...Pure fire!!!