You make this seem like a downplay? Luffy has been fightning in base with a few Haki upgrades and even before , blitzing base Kaido while in base too, also clashing decently against Doffy in base.
Who said Kaido is super fast except outside of Thunder Bagua? His best reaction feat is dodging a G2 redhawk and keeping up with base/G2 Luffy in hybrid.
The point is Mogura has a windup to it - to coil and uncoil the mochi around his arm. And base Luffy (no G2 btw) can do it. Remember what happened in FMI? When Zoro blitzed the dude who made G2 look slow? King was fighting a stronger Zoro in cqc, King obviously can dodge around it. He literally dodged a Rengoku Onigiri this chapter.
That literally changes nothing, a non FS Speedstar user such as Zoro was able to defend/dodge away from the attack. Whats stopping the definitive agile Speedstar of the YC1 group from dodging it? heck I'd say he doesn't even need future sight to dodge it.
Zoro has barrier haki. He didn't dodge it - he blocked it with his barrier haki, the same shit he did when he faced Hakai.
Katakuri doesn't and the range of the explosion is too huge to dodge away in time. Katakuri dodges attacks, he isn't a speed ster mobility wise. And he doesn't have barrier haki like Zoro does.
No matter how you look at it, Katakuri wins against King. Oda indirectly nerfed King by not giving him a good Zoan fruit because his base stats were already so high plus race haxs.
You still don't have an explanation as to how Katakuri would even hurt King in his least durable form.