The Prussians were still wearing distinctly colored uniforms and using lots of close order formations, and in any case Chassepot fire was wholly outclassed by Prussian artillery. By 1914, the QF divisional guns in wide use are going to represent an even bigger proportional share of firepower than rifles than they did in 1870. Once you have practically any fire coming back your way, even if it's just the machine gun sections and artillery, accuracy drops off to almost nothing, especially with bolt action rifles where you can't even keep a shot to shot sight picture. Riflemen, facing an enemy in drab khaki/feldgrau, who advance in open order rushes, using cover and concealment, under a constant rattle of machine gun fire, aren't going to make many hits at all. Past 300 meters, you're really just wasting ammo; at 200 meters, the SMG is a much more effective weapon than the bolt action rifle, since you can shoot so much faster while keeping a sight picture. They probably won't make many hits, but under increased suppressive fire, the riflemen are going to be even less effective at 200m than they were at 300; by <100 meters, a platoon armed with SMGs can drive off a whole company of riflemen.