IT also only works if the soldier is well trained in the things he can do. I can teach you to shoot a machine gun in a couple hours - and half of that time will be figuring out how to shoot and clean it myself (I've used hunting rifles and have enough mechanical knowledge that I think I can figure out the rest - but someone who knows that gun can likely find something I would not figure out). That will be enough for "spray and pray" which is a large part of what a machine gun is used for.

However in a real war you need to figure out what direction to point the gun, and need to know when to fire and when to not. I don't know how the army handles "we are advancing now so don't shoot", or "we are crawling along the ground so make sure you shoot high": someone else needs to give anyone I train those orders. The army trains their machine gun operators better so they can figure a lot of that out without being told.