Well guess what you fucking imbecile having character development, an actual story that matters, and a reason to watch this shit is what would make a good movie.
You are objectively and provably wrong.
1. Character Development: Now, did you mean character arc, or backstory?
A: A character arc is the transformation or inner journey[1] of a character over the course of a story. - There are more than 1 character arcs. Jyn goes from a thief to a rebel with a cause. Bohdi goes from a rebel assassin to a rebel with a concious. Shuttle pilot goes from an imp to a rebel. Chirrut and his boy friday (I seriously suck with names) go from guardians of a destroyed temple to avenging angels. OK, maybe their arc wasn't such a big swing. They all went from people who wanted to live to people who found something worth dying for.
B: Backstory - Which characters do you not know enough backstory for? He didn't dickslap you with it by giving everyone a flashback sequence, but we know the backstory for all the main characters through exposition. It's a common style with anthology type short stories (which I'm pretty sure they specifically said the standalone movies were going to be). It lets you know what you need to know when you need to know it without the story dragging in the beginning.
2. Story Line. You'd have to be retarded not to have seen the story line, but I guess that's all the more reason for me to re-iterate it here. Man captured and forced to build super weapon. He gains the trust of his captors and builds a flaw into it and passes the information to the group that most wants to destroy said weapon. Then the group has to go on a mini mission that concludes with a public raid to get the final update.
3. Reason to watch. Clearly your reason to watch was to hate on it. So once again, mission accomplished.