Strongest currently or strongest all time? This matters, because Sukuna isn't at full power.
"The author said Gojo was too powerful for the story, so he had to be sealed"
Again, for the current story, or the story as a whole? Gojo is getting out of the Prison Realm at some point, so the first claim is actually more valid.
@Cinera @Seth @Luffy is the mc
That's true. But also, no one in the manga acts like a full power Gojo is "beyond" Sukuna. They're close in power, but meta-narratively I don't Gojo will win if they fight.
Gojo isn't the Saitama of JJK. He's the All Might of JJK. And there are characters in MHA who are above All Might.