It's a new game, with new mechanics and a new gameplay concept. They are releasing the content little by little because they want to balance things, it seems logical to me. They want to know how each set of weapons works, make some adjustments and move on to the next. Maybe if they throw them all together they could be outbalanced, this way they can control things better. It's a totally new and fresh content, give it some time. When Splatoon 2 will come out it won't have the same issues, I'm almost sure of it.