WW1, especially on the W. Front was not brutal enough...regardless of the casualties...why? Because the armies continued to fight and the societies continued to sacrifice. Verdun was brutal enough, to the point that the French army mutanied...that was a breaking point.
Yes, usually if a war is extremely bloody, people will look for a political settlement. However, your analysis fails to take into account the different values that are put on the lives of different groups of people. The British forces on the Western front of WWI is a good example of this phenomenon. The West Yorkshire regiment had working class men who had volunteered together from whole towns in its ranks. They and regiments like them saw some of the heaviest fighting.
The people who were profiting off the war (the arms manufacturers) and those who directed it (Field Marshal Haig etc) were aristocrats. The point is that the people suffering were working class and were perceived as "expendable" and those making the decisions and profiting from the war saw themselves as better than them and so had no sympathy for them.
Britain would never have pulled out of WW I no matter how large the losses got. Why? Because the aristocrats who directed the British Empire couldn't care less about the people doing the actual fighting and they were obessessed by the reputation of the Empire. If they had run out of young working class men then they would have sourced more men from the Empire to fill the gaps.
Russia was just as bad during WW I. Sadly this attitude seems to persist in Russia. I mean if the 5,000+ conscripts dying each year in your armed forces were from affluent families, or if they were women, then don't you think the Russian government would be bending over backwards to help them?
Do you remember the Russian woman I told you about who was glad that conscription didn't apply to her, but thought it was good that men are military trained? Well, she's back, she told me that her family were scraping together money to get one of their sons out of the draft. But when I asked her if she wanted conscription to end, she told me no, because it was good for the country.
The point here is some people just look after their own and couldn't care less about the plight of strangers. I have rarely come across this sort of hypocrisy among Britons, but two Russians out of three have shown it to me so far. I also read about a Russian mother who told a human rights researcher that conscription would 'make a man' out of her 18 year old son. I wonder how she will feel if he comes home in a zinc coffin, probably she will just be proud of her sacrifice.
This attitude is similar to that of the Palestinian mothers who are happy for their sons to die killing Israelis. Many "civilized" societies also seem to put a low value on the lives of their sons. Thus wars which mainly kill young men, no matter how brutally, or efficiently, are usually tolerated. However, when they target civilians and so kill people from more precious social groups: women, the affluent, middle-aged men, the elderly, etc then the war becomes far more politically dangerous to continue.
If the world was to end tomorrow I can imagine some newspaper producing a headline like: "World ends tomorrow, experts say: women and children hardest hit" Why do I say that? Because I've often heard politically correct politicians, pundits and psychologists in Britain, say things like women and children suffer most in war blah blah blah. When actually their group is the most protected from the brutal realities of war. You, of all people, should know it doesn't go without saying that every soldier has a girlfriend, or a wife waiting for him at home.