Pacifista isn't a traditional arc boss like Crocodile or Lucci. The Moria & Oars battle still narrowed down to just Luffy.
Both Pacifista and Oars are not a boss that can be taken on 1vs1 and that's why everyone and their mothers ganged up on them.
Moriah was never an actual opponent, he was collateral damage to Nightmare mode while inside Oars.
The small part he had at the end wasnt even a fight, he defeated himself by using Shadow Asgard and Luffy's 2-3 hits only sped up the process and what actually finished him off was not Luffy but the huge tower that fell on him.
None of this matters because Oda will make Luffy as strong as he needs to be to beat Kaido up. Luffy will deal the finishing blow because the story's set for him to triumph over Kaido, not Zoro.
Being strong doesnt help here, his fighting style simply isnt effective and he cant kill people, besides, Kaido is not a guy that is soloed.
Yes, Luffy will deal the "finishing" blow and take Kaido down, Luffy will be down as well, Kaido will stand up 5 mins later, Luffy wont.
The new sword god of Wano is what is going to take Kaido out for good, the same man who brought the national treasure back to Wano.