Just a thought. When we fought set wars, our enemy has logistics backing them up. They had medical units and cared for their wounded. When you are fighting an enemy who does not fear death—who looks forward to it—the wounding aspect goes out the door. It would make sense to adapt a larger, more lethal round.
That is where the 6.5, 6.8, and .300 Blackout come in, but the 5.56mm just won’t go away.