It started with Naruto being the underdog/untalented ninja who wanted to become Hokage
Yeah, Naruto was underdog but the nine tails inside him also implied that he had the potential to do crazy stuff later on. The whole "beast inside the MC" was popularized by Naruto.
And yeah, he became Hokage after fighting Sasuke at the end.
Then Shippuden was all about getting Sasuke back. Then it turns out Naruto was the reincarnation of the sage's son and we all know how that went.
Hagoromo's son Indra and Ashura were fighting against each other. But in case of Naruto, he befriended Sasuke and convinced him to join the fight against their enemies. Naruto and Sasuke, both of them were reincarnation of Ashura and Indra respectively.
As you pointed out, it was not an easy process. Naruto had to go through alot to convince Sasuke.
This just proves that Kishimoto was consistent and planned it all along.
What I mean is that Kishi struggled to keep some of his thematic messaging consistent.
There was nothing wrong with thematic messaging.
Some decisions he made towards the end are debatable, but he had a solid idea of what he was doing.
Giving too much importance to the Sasuke plotline and sacrificing his plot toward the end for the sake of Boruto.
What? You remember that Naruto was Ashura's reincarnation, but have a problem with Sasuke being Indra's reincarnation?
Sasuke completed his revenge against his brother. Narratively, he had no purpose after that. But Itachi played a crucial role in changing Sasuke's decision.
How can you say it was for Boruto? All of the decisions Kishimoto made were consistent throughout the story.
Madara was done dirty, yeah. But he was also using Hashirama cells. White and Black zetsu were there in the story, they were not created few chapters before the end.
It was also showed how Madara was tricked by the ancient script.
There can be things that you personally dont like, but the story was consistent throughout its serialization.