How Naruto's "Otsutsuki arc" lacks on Worldbuilding
First of all: I'm criticizing Kishimoto's work BUT I'm NOT putting him at fault
I'm starting from the point that this was Kishimoto original and intended World setting/building:
That said... I would say that Kishimoto was quite loyal to his plot: Gaara was a war weapon, Naruto became a war weapon (if you look coldly to the "from feared to loved" when he stars saving Konoha, Pain arc was a climax to it), Akatsuki was a good-guys-go-bad because of the system and "to punish the world" they collected their war weapons (the bijuus and their jinchuurikis). It made sense.
Sasuke going all insane also followed that plot-line: the good child loses his family, seeks revenge, finds out his trauma was a side effect of the current system, goes insane, wants revenge against Konoha (his local system representation). It also made sense.
But the aliens' stuff... it's just out of place. If they were really that important... If Hagoromo and Hamura were really someone, wouldn't people say something about them all the time, or at least once? Wouldn't they've celebrations on their memories, since they're the "Shinobi beginning"? Wouldn't exist titles/patents on their behalf? Or on Indra's and Ashura's behalf? If Kaguya was important and bad... wouldn't she still be feared till that day? Wouldn't she be studied at the ninja academy (like H*tler is on our schools)? Wouldn't she be the villain of children's stories? I just don't get it!
But, once again, I can't put this mess as Kishimoto's fault, the whole history got a level that he hadn't planned and, after years of drawing the same characters over and over and over, he just wanted to finish the history, he couldn't think in another way to do so besides "overpowered aliens" and, honestly, even if he could, he probably was just too done with that whole shit.