The progression in this game isn't designed around the ability to complete it within a day. The whole idea behind progression is that it gives you something to do for a prolonged period of time. You really don't need to make 1200 kills per weapon. A large majority of the useful attachments unlock within only a few games of playing with the weapon.
That said, I do agree that there are some problematic challenges in the game that definitely need a change. They are already working on it, but it seems like it's not something that they can easily adjust.