When the dude has literally taken 0 damage on panel and has fought guys with more dangerous offenses than Jinbe like Dabi and Shiggy, this is a pretty audacious claim.
Jinbe in OP is what? A low high tier? That shouldn’t be out of range of MHA top tiers.
Jinbe can't hurt Gigantomachia because he was never damaged on panel by the people who're scrubs to him? You know as well as I do why "No one ever managed to hurt him so he can't be hurt" argument doesn't work.That's some Yonko-fanboy level shit right there. Shiggy fought Machia not to kill him but to make him acknowledge him. If he was going for the kill, he'd have done it during one of Machia's sleeping sessions but that's besides the point. Dabi and Shiggy may have more dangerous abilities than Jinbe but he is far stronger. Dabi and Shiggy have more dangerous ability than Enji too. Do they get a better shot at hurting AFO's over-sized bodyguard than him? Remember Jinbe fought a fire user who can engulf towns in fire for five days.
It doesn't matter how low Jinbe ranks in OP as long as he's strong enough to beat Machina. While it's true Machina is crazy durable, his size is his greatest asset and Jinbe damaged someone 5-8 times larger than him. Just to give you a heads up, Gigantomachina is estimated to be around 25m while Wadatsumi is normally 80m tall with his puffed version being around 3 times larger. I gave you an answer to how Jinbe would deal with Machina's durability btw. Jinbe can damage him regardless of the composition of his body as long as it's made of water.