Nah, it does. It doesn't dig all that deep, but there is some "exploration" there. I don't think "men on a mission" is an excuse, either. That's the kind of movie it is, and those sorts of movies don't really dig too deep into any characters outside of maybe one or two at most. And Rogue One's biggest problem on that front is the character who is definitely the lead is also the character that is, unfortunately, the most wishy washy. I'm sure there are multiple reasons as to why she's that way, but those don't really matter in the face of the overall execution, really. Either Jyn Erso lands or she doesn't, and most of the time, she doesn't. Not as intended. She gets her moments, but they don't feel as solid as they should. There are three instances where I think Jones gets to dig into her role (watching Galen's hologram, yelling at Cassian, making her plea) but she's asked to carry a lot more than just those three scenes.
But that's just one character, and those missteps, while readily apparent, don't nullify or wipe out of hand all the cool character bits that are sprinkled throughout the movie. And there's a lot of 'em. And I feel like they land more than they don't. Donnie Yen, Alan Tudyk, Riz Ahmed, Diego Luna, Ben Mendelsson - they do good work in a film that only gives them so much room to work in, for a director who is like, the opposite of an actor's director, judging by his past work.
I mean, I'm not saying I don't understand why people are like "I can't care" or probably the more accurate "I don't care," I just disagree. It's really easy to care for these guys, and I do.
I wouldn't call Rogue One a "failure" by any stretch. Even the Tarkin/Leia VFX aren't "failures." They're not successes to the extent they probably wanted them to be - but they're not bad, and they certainly don't suck. (or look like a fuckin PS4 game, jesus)
The only thing close to a total failure I can think of is Forest Whitaker as Saw Gerrera. Almost nothing about him works.
But other than that? It's a pretty damned good movie. I really like it.