You are thinking of soldiers actually carefully aiming their shots. During battle few actually aim. It’s more about the volume of fire than aimed shots.
Yes that’s (sometimes) true as well. Notice the M16 doesn’t have full auto anymore, just 3 round burst. Squad infantry tactics have changed though, whether it’s one guy carrying a BAR or an M60 or a SAW, soldiers need a weapon like .30 cal or .30-06; it is not an “all or nothing” situation. It’s just another tool in the toolbox.