Being as you probably play core according to "putting 3-4 bullets" into someone, then I GUARANTEE that you would HATE for the game to be realistic.
Shotguns would obliterate and OHK from about twice as far as they do now
ALL headshots would be a OHK no matter the distance
If a player got shot in the leg, they would hobble and not be able to run
If you got shot in you gun wielding arm, you would drop your gun
in order to knife, you would have to pull the knife out first, and then be able to swipe, meaning NO instant knifing
sniper rifles would NEVER be an option for anything other than long distance engagements
You could not lay down and shoot with precision (dropshot)
Your health would NEVER regenerate
Your precious baby monitor in the upper part of your screen would not be there
you would not be able to survive a direct impact from a RPG/Explosive because you were wearing a vest
you would not be able to throw C4 further than a NFL quarterback can throw a football
There are SO many more, but I will quit here as HOPEFULLY you get the point.
The answer you seek is in the title of this thread. It's the 7th word to be exact, but just so you don't have to go back and count for yourself the word is...."Game". It's a game, that's why they are nor realistic. Like a previous poster noted...You want realism, join the army.
The key to surviving a game is not to go head to head in gunfights. So if you are going that route then you only have accuracy to deal with.
The way to survive in a game is to outflank the enemy and take them unawares.
Problem is not that one gun is more overpowered than another , the problem is that you are using the wrong weapon with the wrong tactic.
Because they are not supposed to be real!
Its an arcade shooter.
If you want realism, you are looking in the wrong place. You dont want realism though really, you just got beaten badly, got salty and needed to vent.
Next time, punch a cushion. Hell, do an Alan Partridge and destroy your cereals even.
To be honest if it were real a couple rounds from anything into you and you would be done.
The guys with SMGs probably had lightweight on. It gives you the ability to dodge bullets.