Actually the Nivelle offensive caused no outsize losses relative the rest of the situation. 1917 was the lightest year for the French army in terms of casualties overall, with only about 150 000+ killed in that year (300K 1914, 350K 1915, 250K 1916, 250+K 1918).France racked up big loses trying to break German positions in 1915 ( Battle of Artois and 2nd Battle of Champagne ) and 1917 ( Nivelle offensive ). The latter even lead to mutinies in French army. They also suffered heavy casualties during Battle of Verdun in 1916, where French were on the defensive for most of the battle. Let's not forget that French losses were high at Somme as well.
The real problem with the 1917 Spring Offensive was rather the sheer mismatch between expectations and outcomes. The French army was assured that finally its leadership had cracked how to fight and win WWI without it all turning into a bloody shambles. And they had the general who had first introduced the rolling barrage in 1915, and the followed it up by kicking the Germans out of the ground they had taken at Verdun in the latter half of 1916, with staggeringly low losses. So now, with all new weapons and tactics, all that was needed to upscale these things, and go blow through the German lines in a war-winning offensive. And then inside two days it all turned into a total pigs-ear, precisely the kind of bloody shambles everyone had been promised it wouldn't become. That led to the refusals to attack, which was what the situation mostly involved.