Sukuna is just spouting bs. He thinks he's invincible, and that Gojo ain't that strong. Though in actuality, they both are equally matched, I'd even go and say Gojo is stronger cuz he used unlimited void more times than Sukuna but they reached their limits at the same time. Prolly proves Gojo has more resistance than Sukuna.
All characters in Jujutsu Kaisen who call Gojo strong are the one who's weaker than Gojo and it's basically almost every character except Sukuna. Even Kenjaku did not try to fight him and seal him instead. Probably because he lose twice to two six eyes user in the past so now he try to seal Gojo as a six user in modern era but Gojo still able to get out. Is Good weak? Well, Sukuna thought he was weak.
so is gojo actually weak? like he's not as strong as everyone made him out to be i'm confused when sukuna says that he's plain ordinary.