I've kind of wondered about that as well. The class that Naruto 'graduates' with is the same age as he is, but if Naruto had failed to pass two times before the first time we meet him, does that mean Naruto started the Academy two years earlier than the others? Or did Hiruzen put Naruto in an accelerated class to have him out of the Academy quicker?
Yeah, there absolutely could've/should've been a revisit of the beginning of the manga to resolve a lot of things in the end. Why Naruto fell for Sakura, what shaped him in the beginning, what happened when he was flunking and retaking the genin exams, etc.
Instead of going back and filling in the gaps on Naruto's story, however, we got flashbacks from HInata's storyline that never happened in the first place. Her getting bullied, her getting saved by Naruto, etc. etc. Thanks. Thanks a lot.
Just as I never doubted that the story would end on NS, I never doubted that Kishimoto wouldn't go back and fill in the gaps on Naruto-Sakura-Sasuke's formative years. Perhaps even a chapter paralleling their early Team 7 missions with their final reunion as Team 7 for the war. How they were the same (bonds) and how they'd changed (NS instead of SS; Sasuke finally recognizing their strengths, individually and as a team). The fact the Kishimoto didn't do this, resolve old issues or bring the beginning of the story full circle, is just a mark of how little he cared about the story in the end.
It didn't matter what he did, because looming behind Kaguya was the biggest villain of all: Hinata. None of us saw that coming. And Kishi no longer cared.