I finished the game and had a great time, for the most part. It wasn’t quite as engaging as Inquisition was for me (my first experience of the franchise). And I think you touched on why: cause Rook feels replaceable. And the main story is like a side quest. Your companions, as BioWare has even said, “are the heart” of the game. But they shouldn’t be. Inquisition was indeed about your companions, but it was still the inquisitor’s story. You were important, central to the events of the entire game. Unfortunately, Rook isn’t that.
This game should’ve stayed as Dreadwolf and focused on Rook’s evolving relationship with Solas. Instead, it’s making sure you solve every problem your team members encounter. It is your teams’ story, not yours. And that feels… crappy.