Wars shows e.g. the cost of resisting the Empire in the very first movie but the blowing up of a planet is fairly abstract. I think that this is simply an implication of the genre, it is hard to tell a romantic story and at the same time delve into brutely honest and graphical depictions of violence.
Clone Wars partly amends at least the abstraction via giving e.g. the clones a human face but it doesn't become graphical.
In general I am ambiguous about the "showing war as it really is" thing. Of course I abhor the sanitized portrayal of war which permeates our media but you can never create on the screen what people really experience in war: heightened awareness, pure existential fear and above all the nightmares that will haunt you afterwards.
Furthermore there is Truffaut's point, that an anti-war movie can feel quite exciting. Take the scene Apocalypse Now when the "cavalry" flies in, despite of all the horrors, despite the movie's crystal clear stance on war the scene is simply invigorating.
It's like when a director considers doing a rape scene. It might be a good idea to not merely imply anything but show the true horror but like in the case of showing killing it can be exciting to watch for the audience. That's why I think that literature is better at showing horrors, unlike cinema it doesn't risk arousing our primitive destructive instincts.
I don't think it is problematic when e.g. Wars or Trek doesn't go all gritty when somebody dies. Picard being haunted by his experience with the Borg or the icy bureaucratic demeanour of a willing servant like Tarkin do perhaps hint at the horrors sufficiently well. Art doesn't have to be realistic to deal with something very real.
Take Robert deNiro in Taxi Driver and Awakenings. Isn't the former one more convincing at showing a person with psychological issues via mere art, acting, than the one which is realistic in the sense of describing a neurological condition medically correctly?
In the case of violence there can also be too much. Unlike words pictures are immediate so the viewer might disconnect or repress it whereas 'hinting at much more' can be more horrifying as you gotta imagine it (which is why children shouldn't watch violence on the screen yet can deal very well with listening to or reading of classical brutal fairy tales like Hänsel and Gretel or Red Riding Hood). A personal example is being confronted with pictures of starving or disfigured children in ads for charity. I don't wanna see this sh*t. But if you give me an article that gives perhaps just numbers about how many people starve I sympathize much more.
This may sound one-sided but I don't wanna argue against realistic violence on the screen. In BSG it was definitely necessary, important and frakking good.
I merely wanted to hint at, writing as usual too much, why I think the issue is perhaps more complex, why realism is not the only option and why the distortions of other non-realistic forms of art are not necessarily bad.