Chris Pine does a really good job, brings his A-Game.
Keira Knightley, well, OK, she is pretty under-rated and ALWAYS seems to bring her A-Game even to the worst possible movies.... and she brought her A-Game again.
And Kevin Costner, well he can be off the mark every now and again, but he seemed to try his best to make this movie good.
And that is why it's watchable. Pine, Knightley, and Costner all bring their best games to this film and do their absolute best to make Shadow Recruit a good movie....
.... and this is despite the HORRIBLE SCRIPT and mostly incompetent direction. Branagh has always been a better actor than he ever was a director, and when it comes to a movie that needs to be taunt and stressful.... they needed someone else.
But then, they also needed a script that could build tension and a director that can work with it, not just do the same trick he failed to execute properly with Frankenstein.
So what you have here are three actors conspiring to save a movie... and unfortunately you need more than three actors doing their absolute best to save a film from a poor script and a poor director.