This argument holds no water.
We rarely saw boundman against Katakuri, cause Kat made it useless. We never saw KKG on WCI, doesn't mean Luffy wasn't going all out. He was getting his shit kicked in, and used all of what he could possibly use.
Right now we know Luffy far more than we do Kizaru, and we know he has used everything available to him in his arsenal. We know he's trying immensely because he is on a strict timelimit.
The prospect of Kizaru having another gear to kick into or even 2, above this, is terrible for Luffy.
Regarding Kaidou tanking all of those hits, Kizaru doesn't tank hits cause he doesn't get tagged, the issue is when he is getting tagged why is he looking like he's taking it better than Kaidou took a red rock without advCoC?
Oda did a terrible job, or maybe Kizaru is just that strong. Because Lucci from a way weaker attack looked like he was halfway passed out mid air.
This might be Oda respecting Kiz, but in doing so he has made Luffy look unimpressive, and the clock is ticking on Kaidou too.