But if one thing should be addressed is the truth behind the Uchiha massacre, Naruto should have exposed it at least, as a means to show that he would be a different hokage than the other ones. He could then also take the elders ( who were never addressed again) out of their position of power.
It's obvious that Kishimoto has no idea on the subject one way or another. Hell on the last interview he said that he didn't decide to make Itachi good until later on. That fact alone shows that at first we have no idea what Kishimoto originally had plan. My guess is that originally the Uchiha were evil, and this caused the most evil one of them to rise up where he ended up killing the rest of his clan for power. Which is what it looked like Itachi did at first. He kept Sasuke around "for fun".
Only later do we learn that not only were the Uchiha generally power hungry and evil because "they love to much", but that Itachi spared Sasuke because he "loved him to much". So basically Itachi had no problem killing his parents and the rest of his family, but because Sasuke is "pure" (there is the kittening stupid phrase again) he couldn't do it.... no mention of any other Uchiha children. I guess Sasuke could have been the youngest but I find that unlikely.
It doesn't matter honestly. Whatever Kishimoto had in mind he changed it, and likely will continue to alter it in order to get the end result he wants, even if it doesn't make any sense,