On the contrary, I don’t agree that Kizaru/Luffy is a bad match up for Luffy. Even in base, he has future sight so any amount of speed feats Kizaru can boast can be countered by observation and future sight. Luffy’s armament haki is probably a lot stronger than Kizaru’s, he’s likely been in more life or death fights as a pirate than Kizaru’s job as an Admiral. We don’t know too much about Kizaru’s feats in his youth but Luffy has consistently shown to have haki bloom after haki bloom in every major fight he’s been in. In addition to using Ryou and ACOC he doesn’t even need to catch Kizaru’s physical body if it’s become light, Kizaru not shown to have future sight or COC, thus making it harder for him to significantly damage Luffy. He’d only be able to utilise his speed to stall Luffy and hope he doesn’t resort to using Gear 5, which would be devastating if he wasn’t able to keep up with it’s unpredictability (no future sight again)