Yes I do agree Luffy wasn't interested on fighting Kizaru like he was with Kaido, but that's one of Oda's many flaws on writting current Luffy, mostly because:
1) Luffy's first ever major defeat was at Kizaru's expense;
2) Kizaru could've killed Usopp had he wanted too;
Which begs to question what the F is Oda doing with Luffy, he should be fighting seriously when his crewmates are on the line, especially the same crew who got disbanded by Kizaru himself once, there's like very few indications that make us assume Luffy was taking the piss with Kizaru.
Yes he did used once or twice, the fact is that he only ever used against Kizaru, and even failed to down him since straight after Star Gun Kizaru helped him, he did not use versus Gorosei/Lucci.
And by the way I do have Luffy > Kizaru, just Extreme Difficulty for Luffy.
My opinion is that with Kizaru's speed, spamming ACoC is not as effective has simple CoA because it will tax Luffy's body and perhaps burn is stamina even fast than usual while using it with G5.
Other Yonko wouldn't have that timer, but we don't know if Kizaru could've won despite the timer or not because we can't actually gauge how strong he actually is. That's why the fight is bullshit.
I believe Oda did not want any concrete evidence as to who was clearly stronger.
If the Admirals have awakening than that makes even most fights retarted in my opinion, or Oda is simply withholding it for something major, but as it stands it's very unfortunate to not see a single Admiral showing a Top Tier power-up despite multiple weaker opponents showing it.
It's truly a shame, really.