WSM and WSC are not the same generation as WSC.
Context is a thing aka the
timeline.
The only true title in the present has always been only Mihawk's.
That's why WSC is a rumor while WSM admits he is a weakling. Common sense 101, Gai-chin.
Nik-chin, the Navy mobilised the entirety of its forces against White Beard. Including the WSS, who in the same battle failed to kill Luffy while going all out by it's own admission.
Grim.
And guess what, the WSS is so negligible that he served under people that you consider beneath him, imagine that.
He took orders by Gorosei and Sengoku AT LEAST.
Talking about
timeline:
At the moment Mihawk remains the world strongest swordsman nik-chin, and you should be proud of your accomplishment through your favourite cartoon characters.
But just like the fastest swimmer is only the best in water, so is Mihawk the best in swords only.
That's why Kaido doesn't even consider him while picturing the strongest, because he is a negligible dot of nothing, an afterthought in the ending of a story of a secondary character.
It's basic logic consecution.
Mihawk is the first in his category, but now that the WSM is dead by mostly Akainu's hand and Godfy defeated the WSC in a fight, where both were helped (Godfy in a stronger measure, but Kaido killed him only through Mr. Go actions), who knows who inherited their titles. We saw BB block with no effort s-hawk attacks, we saw Luffy playing with an Admiral and a Gorosei, while characters with less importance are busy fighting meaningless enemies.
I am sure you will grasp at a 1000 straws. But Mihawk served the government like a dog, and ran away from navy like a puppy, as a fact.
And Zoro, if Oda wanted him to be the strongest, would be defeating strong enemies, not Pica or King or Lucci the 2-times defeated cat.
Sadly, in this case, everything is against you.
Because to this day, the strongest enemy Zoro has defeated is possibly a cat or King, while Luffy defeated the World Strongest Creature. These are facts :(