lmao this thread
The fact of the matter is, Naruto's strongest techniques came from SM and Kurama (not trace amounts of chakra from other Bijuu :lol). Sasuke simply could not match it so he had utilize the chakra of the other 8.5 bijuu. This supposed "immature" rinnegan played little to no role in that fight, Sasuke clearly got a handle of his abilities through fighting Madara and Kaguya and used his strongest ability through Indra's arrow which led to a stalemate (which he could not do without the bijuu chakra).
Also, people need to remember that Naruto and Kurama exhausted most of their chakra throughout the war before the fight even started, so much so that the most powerful Bijuu (which is said to have infinite amount of chakra) had to go to sleep! Where were the other Bijuu to replenish Naruto at that point? :lol
If Naruto had even a little extra chakra to form an oodama rasengan instead of the puny one he could muster at the end of VoTE 2.0, Sasuke could quite possibly have died.
the infinite chakra thing is obviously hyperbole but I'm pretty sure of it being stated somewhere in the series, will look for it if I have time.