We don't want to nitpick. Rogue One was fine.
Alright, let's nitpick just a bit. Character development. You know what makes Star Wars great? Well, light sabers, and the Millennium Falcon, and wondrous planets, and R2D2's beeps, and Yoda backwards talk, and the big reveal, and blowing up the Death Star, and... characters. We love Luke, and Leia (RIP Carrie Fisher), and Han. We understand Luke, Leia, and Han. They are fleshed-out, relatable characters. Even in Force Awakens, with Rey, Finn, and Poe. We get them. We feel with them. Rogue One? Not so much.
Jyn, Cassian, the two Asian guys whose name we don't remember... see, that's the problem, we don't remember their names! They were given back stories, sure, but it didn't make us care for them. And the bad guys! They had to resurrect Tarkin and bring back Vader because the new big bad, Krennic (We had to look up his name, too. Hey, look, the actor who played him, Ben Mendelsohn, is part Jewish!), just didn't measure up.
So, at the end, when (spoiler alert!) the big blast comes, and everyone, from Jyn to Cassian to those Asian guys to Krennic and his ilk die, we don't feel the pain we should have felt. How can it compare to Obi-Won, or Vader, or Han? (Oh, poor Han...)
But we're nitpicking. Rogue One was fine.