Kizaru is the real deal.
I have to agree with OP, Kizaru has earned his praise in this latest chapter. These are literally some of the greatest character feats in the series, and are actually properly scale-able since we know how Luffy fared with these same techniques against Kaidou.
Clearly Kizaru is able to compete with the Yonkou level to a very impressive degree.
Also, for the people pointing out the barrier thing - Kizaru utilizing the barrier (terrain) to his advantage as an attack boon is not poor sportsmanship or cheesy at all. Of course we'd love an uninterrupted "kill or be killed" 1 vs 1 of these two on some isolated island, but that is not realistic. Remember the words of Shanks and even Luffy himself before - "pirates are not saints". Luffy used water to make his attacks achieve against Crocodile what normally would have required haki usage. Likewise we can say "Marines are not saints".
When Whitebeard came for war to Marineford, the Marines didn't stop from using the terrain to their advantage - i.e. freezing the bay, nor did it matter for the pirates that much anyways. (In fact it provided them a foothold.)
This is the nature of the battle. If there is some theoretical terrain advantage to be utilized, the party who uses it is understood to be creative in their fighting methods, and even more dangerous. It is not a shame to do so. Also, the Strawhats certainly did not apply this "1 vs 1 honor" logic in the battle against Oars and Moria.
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Kizaru vs. Kaidou
On the Kaido scaling issue: I would not say that Kizaru's feats take away from Kaidou at all. Remember, Luffy vs. Kaidou was never a 1 vs. 1 to begin with. He was exerting massive amounts of power to levitate an island, was hit with an ambush assassination attempt, survived, fought all of the scabbards simultaneously, fought five supernovas simultaneously alongside Big Mom (and honestly did probably 75% of the heavy lifting against the five on the Rooftop, hence his complaint about Big Mom: "Linlin, you've become an invalid!" - he only shifted into a 1 vs 1 with Luffy after taking multiple hits specifically noted for dealing severe internal damage. Even after all those, he still knocked out Luffy multiple times and effectively killed him once, thus forcing Luffy's awakening. And let's be real - without the CP0 interference thing, it is doubtful Luffy would have won with his G4 Kong Gun anyways, so its not like the interference mattered -it ended up helping Luffy more than harming. Luffy did not even have the ability to tank Kaidou's attacks until G5 massively increased his defensive stats while in that mode. Otherwise he was dodging them or holding them off with an AdvCoC attack of his own.
I would say Kizaru has a strategical advantage against Kaidou on the basis of his speed and the thought that he could theoretically knock Kaidou into seawater with his techniques. However, Kaidou is known for defensive stats and durability and could probably take many, many hits from Kizaru without a great consequence. Landing a hit would be more challenging, but he probably doesn't need to land too many successful hits to take down Kizaru. It's not a given that Kizaru would defeat Kaidou, let alone "low diff" him. But it would probably be an epic fight.
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Be careful if you claim "Plot Induced Stupidity"
Also, on the thought of any P.I.S. claims - theoretically if Kizaru could grab himself a pair of seastone handcuffs, or utilize a seastone weapon like Smoker or perhaps a seastone injection tool like Stussy - then he would have the greatest utilization of such items because his speed guarantees he would have a perfect chance to nerf his fruit using opponent with him. For example, if he had a pair of seastone cuffs on his person - that split moment where he kicked Luffy into the barrier, instead he would have cuffed him and drained him of his energy. If anything, Kizaru is not even operating at his theoretical optimal by refraining from handling such items.