The Iliad is based on an epic conflict, the Trojan War, so of course war plays a major part in the poem. Homer presents war as a testing-ground for heroes: a place where brave soldiers can write their name in the annals of history by performing heroic deeds on the field of battle.
At the same time, however, Homer is unsparing in his account of the horrors of war. His detailed—and at times lurid—descriptions of the heat of battle leave us in no doubt that war is hell. It's notable that Hector, the Trojan prince, is presented in suitably heroic terms for trying to minimize losses on his side.
His concern for saving lives is contrasted with the gung-ho attitude of Achilles, who dives straight into the thick of battle without any thought for the safety of those around him. Everyone else can die as far as he's concerned, just so long as he can achieve glory and avenge the death of his bosom buddy Patroclus.
As to whether or not all this bloodshed is worthwhile, Homer gives us the impression that it isn't. The cause of the war, Paris's elopement with Helen, is relatively trivial, and it's notable that at one point the Achaeans are just about ready to pack up and go home.
Even if the cause of the Trojan War hadn't been so relatively unimportant, it's unlikely that there would be any justification for such wholesale carnage. Furthermore, it's not just soldiers who suffer from this conflict. Hanging over the heads of the besieged people of Troy is the grim realization that, if the Trojans lose the war, all the men inside the city walls will be slaughtered and the women and children sold into slavery. It's difficult to argue that this would be a worthwhile outcome to any conflict.