Chakra didn't vanish however the ninja world basically embraced new mindsets and ways of thinking, loads of countries individuals actually experiencing the occasions of that conflict with Obito/Madara/Kaguya/and so forth
Individuals having confidence in ninjas and ninja ways gradually vanishing and a better approach to manage issues seemed which is science (logical ninja apparatuses), intending that, ninjas are on the downfall even in Konoha, it resembles an entirely different period, consider it the section from the medieval times to a more present day like time (creator sped the cycle too quick though) and with Naruto zeroing in alot on work area work (his abilities as Ninja relapsed and he utilizes the powers of Kurama alot) Sasuke's work is essentially spying and going around really looking at stuff.
Basically with the demise of the old age and a considerable lot of the notable ninjas, the ninjas and the ninja age is gone, it is another period with new convictions and perspective on the world (in harmony, as the new ages live in a superior more leisury world) yet with more otsutsuki in it, the time of legend and unnerving followed monsters is gone, it is the time of ninjas with science(chakra controlled science) against outsiders.
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