I think oda has to be VERY careful with this though. With Doflamingo it was clear Luffy was overwhelming him and fully surpassed his caliber of pirate.
Kaido is supposed to be the strongest, if not one of the strongest pirates in the series. Future fights will probably be more horizontal progression than straight vertical progression in power. Luffy, in any form, shouldn't "overwhelm" Kaido, because that would imply he'd far stronger than the WSC in that form.
It's good that the fight is taking a while. It's meant to be brutal and long for the specific reason that he's not meant to defeat his opponent in a few big hits here.
Yea but him being careful only sacrificed Luffy again and again, since he's way too afraid to kill or severly cripple other important characters when he beat them. Zoro, Law, Yamato, even Scabbards, all were exempted from death. Imo this is the main cause Oda always gave Luffy a repeated loss, since he's the only one capable of enduring it without being dead in the process, while others get super recovery medicine, being split by Ope2 before being CoCsmacked which saved their life, other deus ex machinas just after being.
But in doing so, Oda sacrificed tension for Luffy and also for everyone else since there's no sense of danger anymore. Since Kaidou's threat will always be aimed at Luffy, and fear not, Luffy will get one powerup after another since Oda is confused how to solve this problem without wasting 10 hyped but also plot-restrained powerups for Luffy.
If only i can get in touch with him via Greg i would honestly criticise and give him ideas about power progression for MC.