I still don't see Luffy soloing Kaido in 15 minutes. Oda acknowledged Katakuri's strength by making him fight Luffy for 10+ hrs. Kaido is the WSC and the king of 1 vs 1 and you want me to believe he falls in 1/4 hr, I understand that he is a bad guy but that would be the ultimate disrespect. This is shaping up to be Kaido vs Strawhats, another callback to Thriller Park
Another point is the ongoing theme of relying on your individual strength against relying on others. The Oden flashback presented Oden as someone who wanted to carry all the burdens of Wano by himself and didn't ask for help from his 9 scabbards (just like 9 Strawhats) until it was too late which eventually resulted in Wano's ruin. That theme also shows up again with Momo, Robin, and Sanji. It would be very weird if Luffy beats Kaido through sheer individual strength
In WCI and even though it was Katakuri that Luffy fought against instead of BM, the main thematic battle of the arc was between Luffy and her. Luffy who was ready to fast till death if it means that anyone other than his friend prepares the meal for him and was satisfied with it even if it was terrible because it was Sanji's meal against BM who is very selfcentred and is ready to sacrifice her family and allies to satisfy her urges and is not satisfied unless it is the best cake, that's why she ended up losing against Luffy, that was a conclusion to the addiction theme of WCI. Usually there's a thematic battle between Luffy and the main antagonist of the arc that Luffy triumphs in. Kaido is a pirate who believes in individual strength, that has been highlighted times and times again, if he loses in a 1 vs 1 battle then it doesn't help the themes in anyway
Luffy was overconfident in his last time against Kaido and tried to finish it all by himself which resulted in him losing and the narrative mocking his cockiness through Kaido. Kaido will lose because Luffy will ask for help from his crew when he comes back
