Realism shouldn't make weapons redundant if properly implimented but unfortunaltly realism is just applied to weapon damage and sometimes recoil which tends to make the weapon of choice the one that does most damage with least recoil, with highest rate of fire and largest mag capacity, usually an assault rifle which by strange coincidence is the weapon of choice for nearly all the worlds armies.
In the real world assault rifles do have down sides, they're usually long and not great for storming buildings or using in vehicles, you might prefere an SMG for this role. They're not the best suppression weapon, the round is too light and they dont have a great enough mag capacity, you want a Medium or heavy machine gun for this job. Suppression doesn't work well in games in any case, people just arn't afraid to die, they wouldn't be as brave if the bullets were real.
Realism is unattainable really, how do you model fatigue, fear, body armour preventing you from holding your weapon properly, condensation on optical sites, gas masks messing up eye alignment, your rucksack sliding forward and pushing your face into the ground, the ground being uneven and slippy......... there's too much to model.
