I am not literate. What I meant was I think Sai is a superfluous character.

I think the plot of a manga has different phases. When Gaara appeared, the viewer is still in the exploring phase, where Naruto still had no real main goal/mission. But now, Naruto has a goal. And when a character pops out like that, it becomes superfluous. It seems that they just impeded the plot by creating branches. I think the general feeling is that we are not in mood to learn a new character:

what's the point in introducing ANOTHER character when there are already like 20+ to choose from? it's just stupid.
While there aren't that many conflicts. I think Sai is just introducing a superfluous conflict.