So if it were Katakuri instead of Marco who led the remnants of WB pirates in the payback war. Do you think BB wouldn't be considered a Yonko?
If it was Kata who led the WB pirates B.B. Would have been considered a Yonko too. Because beating a high high tier with a pseudo (below a real one but still strong) Yonko crew behind him is worthy of being recognized a Yonko.
But does that change the fact that Marco has a particular portrayal ?
Any RH (except prime Ray) in Marco shoes would have lost against BB, does this mean Marco and Kata and Ben and King are equal just because they all lose to BB ?
And even if we say that Kata in the same situation would have done the same or better who knows because Oda wrote all these scenes and all these moments for Marco.
This is portrayal
Does Kata can fight admirals ? Maybe but Marco did it
Does Kata can lead his crew and fight BB the main (or second) antagonist for him to become a Yonko ? Maybe but Marco did it.
Does Kata would be considered important to help and be looked after to fight against Kaido in Wano war ? Maybe but Marco did/will do it.
Maybe Shanks would have asked Kata to join him but in the real manga he asked Marco.
Oda chose to put Marco in all these situations and moments and we can ask ourselves if others could have done it but the one who was chosen was Marco, the one with feats or relevance was Marco. The big bro of Ace was Marco, the RH of WB was Marco, the guy who fought the 3 wars we have seen in One piece is Marco.
All of that makes Marco special, this portrayal as someone important in the One piece world.