I'm on chapter 7 now and I think the bolded is exactly why reviewers knocked the game. So far, from chapter 1 to chapter 7, it's all been pretty much the same thing, kill bad guys, advance further,
Haven't played it yet, but based on impressions I'm guessing the reversal of expectations likely played a role, namely that Knack's size shifting was made out to be such a distinguishing trait, but in the end gameplay remains largely the same regardless. I'm still debating whether to keep this or return it when it arrives, but leaning towards giving it a shot.