Let's REALLY look at their weapons.
Tahu has two sticks with a sword at the end.
Pohatu has a stick with a sword at the end.
Gali has a stick with a sword at the end
Lewa has two smaller sticks with a bigger sword at the end
Kopaka has a smaller stick with two swords at the end.
All of their weapons are basically the same thing with some slight deviation. Oh wow! Tahu's sword can flip out! How unique and special! Woah! Pohatu's staff has a boulder at the end! Amazing!
Are you really arguing 2015's weapon line-up is worse than 2016's? Sure, Tahu and Kopaka shared the same blade piece and Lewa and Gali shared the same ax, but the way they used said pieces is what made their weapons unique. Tahu had two giant swords while Kopaka had a formidable shield. Lewa had twin axes while Gali had a giant trident.
All of the weapons felt unique and different, something 2016 totally lacked.