I think the writers didn't bother with character development since everyone not part of the OT dies at the end. I enjoyed the movie because it had what I want in my SW derived products, as is a group travelling across a few different planets and having various adventure there. But I felt that it hewed to close to the first SW, unlike Solo, which took more risks, but still managed to be predictable
I've heard this excuse before but it really makes no sense to me.
If the point of the movie is that these characters all sacrifice themselves at the end for the Rebel cause, then all the more reason to develop them as characters so that the audience actually gives a shit when they die. If the writers didn't even care enough to give them characterization then why am I even watching? It could have been
Jan Jyn and 5 random rebel soldiers and it wouldn't have made a difference.
Besides, there are some character moments that are clearly meant to be emotional and impactful - they just fall flat because they feel so unearned. So I don't believe this was a deliberate choice to have no character development, I just think they were lazy. If they really intended for this to not be character-focused then there is no reason for the first half of the movie to exist.
And it's not like the plot makes up for lack of interesting characters, because there's nothing clever or unexpected there either. You say Solo was predictable but it at least tried for some twists and turns to its story. Rogue One couldn't even be bothered to go through the motions. The visuals are nice, but there's no substance to anything that's happening.