As a SW fan, I really liked Rogue One. Much better than Episode 7, which ranks below the prequels in my book. I actually had quite low expectations for Rogue One since it's shoehorned into the story and we already know how it ends. It's ironic that Episode 7 could have literally done anything and came up with a tired and unexciting story. Rogue One was written under very tight constraints storywise and yet came up with a plot that felt fresh and exciting. The original story was expanded in a way that convincingly explained some plot holes without creating more. The universe got deeper, but not in a way that seemed to contradict the original.
That said, I agree with the assessment that none of the characters were particularly exciting on their own. It seemed that the movie didn't really dedicate much effort to developing them, which in my opinion was a good choice. There was a fair bit of fan service, but it was mostly well done.
The one part that bothered me was Darth Vader. His cape was cut quite differently in a way that makes him look smaller and less imposing. His final scene relied too much on CGI. It just felt flat too me. I would have appreciated more practical effects in that scene.