I think people just don’t understand what the term weakness means.
In comics, often weakness just means their powers don’t protect you from it and makes you a normal man it doesn’t mean you take double damage from it.
For example:
Bondage for Wonder Woman - It doesn’t kill her just takes her invulnerability away
Color Yellow for Green Lantern - it doesn’t kill them just their power rings and constructs couldn’t defend from it
Magic for Superman - It doesn’t do double damage to it he just has no natural invulnerability to it.
This is what cutting and piercing attacks are to luffy. It’s a weakness as he has no natural protection against them. It’s not like sea water tho
In comics, often weakness just means their powers don’t protect you from it and makes you a normal man it doesn’t mean you take double damage from it.
For example:
Bondage for Wonder Woman - It doesn’t kill her just takes her invulnerability away
Color Yellow for Green Lantern - it doesn’t kill them just their power rings and constructs couldn’t defend from it
Magic for Superman - It doesn’t do double damage to it he just has no natural invulnerability to it.
This is what cutting and piercing attacks are to luffy. It’s a weakness as he has no natural protection against them. It’s not like sea water tho