What sasuke did with the bijuu was tapping their chakra source only for his finisher move.
That is like calling G5 a finisher move. With is simple wrong.
Strong Susanoo was able to fight off Asura Kurama Naruto, not his normal Susanoo...
Here as example Sasuke normal Susanoo vs One Kurama Naruto(not Asura):




You see Naruto in Kurama modus vs Sasuke Susanoo was a equal battle.
But this changed after Sasuke used the bijuu chakra to make Susanoo the avatar of the chakra of the bijuus, made Susanoo far stronger(Six Path Rikudo lvl based on Kurama):

And this is how multiple Kurama mods fought Rikudo Susanoo Sasuke powered up:







This is clearly not a finisher but a entire new form, he used to face Naruto and overpowered him in mutliple combat situations...
You can clearly see difference between normal Susanoo Sasuke and the one who got a new form by the chakra of the Bijuus...
And you see how Naruto himself powered up with natural power, he got also stronger by his own skill.
And this is how the fight ended:



So explain me how Sasuke is strong as Naruto?
Without the Bijuu chakra he got, could he really face Naruto?
Let be honest, his perfect Susanoo was blocked by one Kurama Naruto...
Multiple one would overpowered Sasuke, let alone Asura who matched his Rikudo bijuu version..
If Sasuke didn´t had the bijuus, this is how it would look like:
Asura Naruto>>Multiple Kurama Naruto>One Kurama Naruto=Perfect Susanoo Sasuke
It is clear that Naruto was clearly stronger.
He was the one who keep up with Kaguya while Sasuke was not.
He was almost immortal while Sasuke was... well Sasuke..
Asura Naruto mid diffs Sasuke at worst..
Only via Bijuu chakra Sasuke was able to keep up with Naruto.