Because Rayleigh is very skilled, a haki master and forced him into close quarter combat, where Rayleigh is still a master swordsman, prolly gets even retconned as being an advCoC user.
Meanwhile Kizaru can jump around BM and laser spam her ass. No agenda whatsoever, that's just how it boils down right now. If she gets hit by all that stuff, she's practically target practice for Kizaru, regardless of porttayal.
He's additionally immune to her elemental homies btw.
It's on Oda to back up portrayal.