Never really a good idea, sometimes just the only option. As in WWII, which was unavoidable and had to be done. WWI, however, was a terrible, terrible idea all around and just should not have happened at all, and if it didn't, then WWII probably wouldn't have happened either.

In that case its not the war that seems pointless to me but the loss of human life. The average German solider wouldn't have conceived a plan to exterminate entire nationalities by himself, but he was manipulated into killing and dying for that cause.