Because he knew naruto was too strong for sasuke. And also he knew naruto naruto wont fall prey to sasuke's overall jutsus. -ameno? foot speed negg diff
-chidori? base rasengan counters
-enton chidori? base rasengan counters again
-genjutsu? ibtch please
-pain's path? he survived pain twice
-amaterasu? a rookie samurai survive that "hotter than the sun" jutsu for more than 30 seconds.
the aforementioned were what hagoromo considered and then decided not to tell naruto of the potential threat he faces
Bold:
1. Sasuke did use genjustu on what he needed and it worked.
2. Sasuke doesn't have pain's path.
Hagormoo was just going on by history and luck, he really has no big concerns for children he did not bare. Indra and Ashura are just ghost.