With the way gunplay works in U3 it seems impossible to fix certain weapons into being “viable”. If anything, we should be thankful that there isn’t just one meta weapon - instead as you said, its three different weapons.
I commented it on another post, that if Nelson wants to “rebalance” guns so that all guns are viable, then he shouldn’t nerf existing meta weapons to be worse, but rather buff or improve scenario-specific weapons like SMGs and Shotguns in some way to be useful for their respective situations.
This way, lazy people like me can continue to do a jack-of-a-trades generic maplestrike loadout, while others might get an edge on me by using the most effective weapons for the situation.
I suppose thats a bit off topic but yeah, complicated subject.