The harsh realities of a galactic civil war were on display, in this Star War Story. We are introduced to a band of rebels, and many of them have very impactful moments.
One of the themes of the film is self sacrifice, for the greater good. The crew of Rogue One constantly face choices that put their lives in danger.
Throughout the final act of the film, the fate of the rebellion, at several points, rest on the back of one person. If that one person fails, the rebellion fails. These moments make each of these characters important, as they attempt to complete their part of the mission to steal the Death Star plans.
"We'll take the next chance, and the next, until we win, or the chances are spent." - Jyn Erso
Some parts of the battle on Scarif are reminiscent of war movies such as Saving Private Ryan. In that film, many of the characters also sacrifice themselves for their mission.
Beyond films sacrifice is also just a part of war, in real life. Men and women sacrifice their bodies and even their lives to fight for their nation or for their freedom from tyranny. As the saying goes, "Freedom is not free."
The crew of Rogue One do what needs to be done, when noone else, including the Rebel Alliance will do it. They are galactic heroes, in the truest sense.
"Greater love hath no man than this, that a man lay down his life for his friends." John 15:13 KJV