The problem with it is precisely that it is functional. It's a system based upon the very real need to take cover when someone is shooting at you. Unfortunately, it leads to the exact situation real soldiers face: it's repetitive. Once the best methods are figured out, tactical warfare becomes a process of using them over and over again. And this is aggravated when there are chest-high walls everywhere and levels are strictly linear.
Real-life soldiers at least have the options of a variety of grenades, rocket launchers to destroy cover, incendiaries to burn the enemy out, smoke bombs to provide concealment, and the ability to flank around particularly thorny fortifications. Or, failing that, call in the air support/artillery/armor to flatten the enemy.