I have a hard time understanding these complaints about R1. I thought Jyn was a bit bland for the lead the first time I watched it, but I’ve come to like her more the more times I’ve watched it. Otherwise I think all the characters were great and I agree that I enjoyed finding out who they were and where they came from through their interactions with each other. We don’t need to know everything there is to know about each of their life stories for this film. The film gives us exactly the info we need to understand their motivations and choices as they relate to the plot of THIS story.
I think (despite the turmoil or whatever behind the scenes) the filmmakers did a masterful job finding that right balance of giving us enough about them without bogging the film down with a bunch of back story exposition.
As for Cassian, I’ve always found him to be a compelling character. Like someone else mentioned, a rebel who’s willing to cross the line for the greater good is something we’ve not really seen much of and he feels like a real person instead of an archetype. And the pairing of him with K-2SO is wonderful. They have a great dynamic between them and I can’t wait to see more of it!
Oh, and Vader was perfect in R1. Everything he did and said felt perfectly in keeping with what we saw in the OT. Was it really “just his presence” that made him intimidating in the OT? Not the fact that he choked people with his mind, single handedly shot down a big chunk of the rebels’ fighter pilots, caught laser blasts with his hand, used the force to pummel Luke with stuff he was ripping out of the walls, and so on. But yeah, Vader is only cool and intimidating when he just stands around breathing at you. I swear some people just don’t want to have fun anymore!