Ooooh the massacre. Yeah, I thought it was a really good element to start, but by the end, it was so muddled and twisted that it lost its impact in the story.
It's used to justifies Sasuke's lust for revenge, yet Obito never is held accountable for being responsible for it. And Itachi goes conveniently from killer to saint, with everyone forgetting that he was the hand that dealt the blow and tortured Sasuke for years afterward.
It could have been a touchstone in the story for Kishimoto to have gone back to — Sauske's emotional wound could have been healed in the end, and the people of Konoha could have finally understood the terrible bloody past of the Uchiha. There could have been forgiveness and resolution. But we got none of that.
I just recently read a fanfic where Sasuke can't come back to the village because he's still hated (because Kage Naruto won't exhonerate the Uchiha name because it would make waves with his in-laws and the other powerful clans). And so since Sakura is still in the village with Sarada (who is Karin's child in this fic), Sarada bears the brunt of all the hatred of the village. She basically is treated like young Naruto was! Now, this was a fic, but wouldn't this same scenario be happening in the village in canon? Sasuke's left his daughter in a village that hates him and his clan. How is this going to end well?
And Itachi...I always thought he was a much better villain than the sudden saint who seems to know everything about everything and NOW wants to tell everyone...after he's killed his family and twisted the mind of his only brother!! Lol. Itachi as the patron saint of "Don't-question-me-I-know-what-I'm-doing-now-do-what-I-tell-you-to-do" is a much harder sell than Itachi the Villain. Itachi the Villain was much more clean cut. In the end, Itachi was turned into some kind of psychopath moral compass, popping up to tell Naruto how to be a good Hokage. As an ultimate ninja and cold-blooded killer it was easier to understand him — but when he turned "good" that's when things went bad. No matter how Kishimoto spun it, you can never use committing a massacre to justify anything. Ever. Itachi was a killer was believable. Itachi as a savior was too far-fetched. It turned the whole focus onto his motives instead of his actual crimes, and it belittled the people/family/friends/lovers he murdered.
Then back to Obito...in the end, there was very little mention of his role in the massacre, as well as in all the other murders: Naruto's parents, the other jinchurikis, YahikoKonanNagato, the Mizukage.... All of it just swept under the rug. Obito got the magic-wand Itachi treatment, and all his sins magically disappeared. And we end with Naruto calling him a cool guy. *shakes head*
Anyway, like I said, the massacre could have been an anchoring moment in the story. Something for Sasuke's evolution to hinge on, and something to help bring him full circle. Hell, it could have worked for Naruto as well, using the massacre as a small-scale version of how violence begets violence and how he wants to stop that cycle. But none of that happened. Naruto didn't stop the cycle, just like Sasuke never got to exonerhate the Uchiha name. His clan's massacre just got lost in the scattered marbles of this story.