comparing buggy becoming a warlord /emperor to nami hurting luffy without haki is disingenuous. we know nami shouldn't be able to hurt luffy without haki , while the events that lead to someone becoming an emperor is less clear-cut.
you can't create exceptions when you want
if it was about individual strength then there are many pirates that could fill that void, kidd and law being two . Oda has been building up buggy as fairly charismatic leader going back to mf leading a pack of notorious prisoners in impel down, recently we found out he had giants in his group and over the course of wano he probably got even more powerful allies.
That's what being a yonko has always been. coincidentally most of them have been the amongst the stongest pirates but it was never a necessity . this gatekeeping around what it means to be a yonko/yonko level has really been stupid.
Buggy is literally a gag character, that's his existence, he might as well be Oda's self insert with the level of plot armor he has, him being a Yonko is no different from Nami hurting Luffy/Zoro, it happened because Oda wanted it to happen and thought it would be comical.
It's not an exception, Buggy being made a Yonko is clearly a gag, like, you have to be delusional or in denial to claim otherwise
- His crew is straight fodder and we know this because Hajrudin who was one shot by DR Luffy was one of his strongest members
- He has zero known territory
- He's far, far weaker than even Enies Lobby Luffy
There's not a single thing he has that could make him a Yonko except plot armor
To claim you don't need to be strong to be a Yonko is just plain retarded, when we're first introduced to them as a concept they're literally referred to as the strongest pirates in the world by Garp, pretending that you only need a bit of notoriety and a fodder crew to be one is joke worthy.
Also you're clearly misinterpreting what I'm saying, I never said being strong individually was all you need to be a Yonko, you obviously need a decent crew and other things as well.