Because Plot, that's why..
Naruto has all 8 bijuu aswell just so you know.
You didn't even give naruto rikudou chakra.
Bijuu absorbed + Sharingan/Rinnegan + Hagoromo's chakra = Bijuu/Jin + Massive amount of senjutsu + Hagoromo's chakra
Their powers are equal, sasuke's bijuu absorption is compensated by naruto being a perfect jin & having a ridiculous amount of senjutsu.
naruto has a part of their chakra(and its not even a lot) he doesnt "have them" as u say
Just like Naruto used the Plot to get to Sasuke's level a lot of times from beforeThis too, plot helped Sasuke get onto Naruto's level.