Yes, Wano is Zoro's arc. And that has been foreshadowed since Wano was introduced with... Zoro vs Ryuma. There has been very clear build up, from its first mention, of Zoro playing a huge role in Wano. And Oda has delivered on that, because we're now in the situation where he's been armed with the sword of the rightful Shogun and aims to kill the usurper. That's his own, distinct plot, a vitally important one.
But arc's don't just have one character that they revolve around. That really hasn't been the case since... Alabasta? WCI was Sanji's arc- but it was also Jinbei, and Pedro, and Carrot, and Katakuri, and Big Mom, and Capone's arc. And Dressrosa was Law's arc, but it was also the Grand Fleet, and Doflamingo's, and Fujitora's, and Kyros, and Rebecca's. And Elbaf will be Ussop's arc, but we can be sure other characters will be involved as well (Hajrudin, Lola and Big Mom already having staked a claim as well)
And Wano in particular is huge, because it's the culmination of every single arc since the timeskip. There's a lot of storylines to be wrapped up here. It's, narratively speaking, the biggest arc One Piece has had since Marineford. There's a lot of characters that need to shine, and for some of them, it'll be for the last time. Zoro's moving on after this with the rest of the crew. Most of the other characters here aren't.
As for Kid and Law- so far in Wano, they've been overshadowed by Luffy, Zoro, the Kozuki's and the Red Scabbards. Law's contribution has been nagging at the alliance and having an on going fight with Hawkins. Kid has done even less, he's just ran around Udon and got freed by Luffy's alliance. They have been set up to attempt to take down Kaido, but I've seen nothing to suggest they'll succeed. They are characters that Oda's hyped up, so you'd think they'll at least land one decent hit on him, but more than that? Very doubtful. And quite honestly Zoro's got just as much build up to do that much as those two have.
Kid I have more hope for, because Law's already had his arc and Kid, from Saobody, was meant to be the bigger dog, comparatively. Overall contribution to the plot of Wano though? Zoro's got them both beat, hands down.