Disagree on the Lucci and Kaku thing, they're not meant to be far apart although Lucci is obviously superior.
Also, Zoro never really struggled with Lucci. Once he used an actually strong named attack Lucci nearly died.
So it's fine if Sanji fights Kaku as long as it's in a similar manner to Zoro vs Lucci where once Sanji whips out an especially strong move like Hell Memories (even if it's just DJ) Kaku is finished.
I do agree that Sanji should have clashed with Kizaru a hit though. Obviously Kizaru would beat him without much trouble in a real fight but a few clashes never hurt anybody.
It's nuts that Oda had Zoro knock Nusjuro on his ass and then had Sanji do a far less impressive feat against that same top tier, as well as to go as far as to have him get clapped by all the other top tiers on Egghead. He's gotta do more if he's going to keep portraying Sanji as Zoro's near equal.