Big Mom didn’t even use basic armament until the very end, and even that was just against law.
And yeah, Luffy got oneshot by Kaido at the start of Wano. Which means that Kid is at most around the durability level of Whole Cake Island Luffy. Which is YC1. Which, to a top tier, is basically fodder.
But Kid acted like he was actually a threat to a Yonko one on one, and was upset that Luffy was the one who became a Yonko instead of him. He had far more confidence than he had earned.