I don't want this to turn into another debate about whether Ninjago is good or not, but I will say this:
I understand this is a viewpoint that many people have, that Ninjago gets "repetitive" in its sets, but I, for one, am not entirely bothered by this. I don't go out and buy very many sets, so I don't feel that much obligation to go out and buy every single Kai mech they make. I just like to see the different takes each wave has on the vehicles, and the different styles and color changes between years of story. And I do not doubt that if Ninja 1998 continued for longer than a year, it likely would have fallen into a similar pattern of "repetition" that people criticize Ninjago as following. Not to mention that 1998 was restricted to only one style, so the number of possibilities would be shrunk farther down. (Also, am I reading into this right, or is this a sub-subtheme? It's not super comparable to Ninjago if that is true.)
However, the more unpopular opinion I have regarding the accused repetition is that saying "Oh, look, another jet for the blue one," is similar, though arguably not analogous, to saying "Hey, look, they made another red fire one," to every wave of Bionicle.