I don't think it was inconsistent. I think it was just Kaidou getting more and more excited through the course of the fight meant he wanted to take more and more powerful blows.
Plus the Red Roc was something Kaidou wasn't expecting, but it didn't seem like he was really affected by it,
It just feels difficult for me to get a frame of reference for Luffy and his attacks if we're just meant to assume Kaido was sandbagging through the early phases. aCoC is supposed to be seen as an amazing power-up for the very best, yet Oda failed to convey that for me when none of the attacks Luffy was landing seemed out of the realm of what he was dishing out before, and many of them got less of a reaction out of Kaido than before he unlocked the power-up.
Also how the various gears failed to shake up the power dynamic in a real meaningful way. Base Luffy fights Kaido for a dozen or so chapters on relatively even footing. He goes G4 and continues fighting Kaido on relatively even footing. He then awakens the legendary G5 and the fight continues to be a fairly even back and forth. Gear 5 did the most, but relative to Kaido they didn't really do enough to fully differentiate the dynamic between them, and it has led to base Luffy getting overrated because Oda didn't do a solid job conveying the differences between forms.
Looking at Luffy vs Lucci in EL
-Base Luffy was on par with base Lucci going blow for blow, but failed to deal any noteworthy damage and struggled to keep up with his zoan form
-Gear 2nd Luffy flips the script, he is now visibly much faster and stronger than Lucci and his blows are now having heavy impacts that are wearing him down. Lucci isn't able to keep up until the stamina drawbacks kick in and start providing diminishing returns.
-Gear 3rd delivers absolute devastation and it's clear Lucci wouldn't stand up to another hit, but he gains back the speed advantage and can outmaneuver the form.
In this fight it's made abundantly clear where Lucci stands relative to each gear in terms of strengths and the advantages/disadvantages he has over each. Kaido fight felt far more stagnant in terms of progression despite juggling far more power-ups and forms, and I find it difficult to scale from that when base Luffy dances on a Thunder Bagua while G4 and G5 can't seem to avoid an attack to save their lives; or when an aCoC Overkong Gun gets shrugged off like nothing after dozens of chapters of Kaido reacting like a drama queen from what should be massively weaker attacks.