It's an ending
Been very much looking forward to this coming out, Jay's had a lot of stuff on his plate which resulted in the delay of this book until now ... and think it's suffered for that and the various rewrites it's had.
The previous BotS books have managed a decent pace to them, usually building up to a finale with a touch of motivation, belief, crazy idea, fighter pilots doing the unbelievably crazy stuff. This book in particular needed to spend time in the characters heads trying to understand all that, but that balance was off in this one. Without spoilers, there's one character who says they regret not being assertive enough sooner in one chapter, only for near-enough the same words to be repeated by the same character two chapters later, and so on until the final chapter where he says the same thing out loud to another main character. That sadly applies across a few other characters too and spoils the flow of an otherwise excellent idea.
It's an ending, possibly not the finest, but it's an ending at least.