Old characters turn into fodder as a way to make these new "emerging" characters that have room to grow in the series look good.
As if anyone in Konoha other than Naruto and Sasuke can even do anything against these so called "antagonists" of the series that are capable of wasting who were supposed to be the absolute god tiers (with feats to match) that were established in the previous manga.
Naruto ended, The Seven Deadly Sins ended, Toriko ended, Bleach ended, Attack on Titan Ended, Black Clover abandoned us, Berserk's author died, I fear one day Oda is going to die, and who knows wtf is going on with HunterXHunter anymore lord knows I don't.
Let me keep Boruto. I don't have much left and I'm getting old.