It is quite telling that Luffy defeated Kaido and yet there are Luffy fans who think he still hasn’t proven himself and needs to defeat Kizaru for him to prove himself
That's because gear 5 Luffy never defeated a fresh kaido
Kaido was lifting an island
Fought Zoro killer kids law and Luffy since they were mostly aiming their attacks at him and not big mom
Then even when law and kidd focused on big mom Luffy and Zoro focused on kaido with Zoro giving kaido a permanent scar
Afterwards Luffy fights him more awakening advanced coc
Then afterwards he losses again and Yamato fights kaido also using her devil fruit and advanced coc.
Luffy gets back up due to food and then fights kaido along with Yamato.
Then Luffy 1v1s kaido that has already been through all of this and losses again.
Only for Luffy to come back in gear 5 and then afterwards barely win