That's because outside Jack, she didn't have a personal grudge against Kaido like the Dukes did. They have more history with not only him, but Wano as a whole. Just saying she feels like a side character doesn't mean she'll stay in that same position. The goal post always shifts in regards to Carrot to describe her presence in the plot when, as we've said before, you don't know why she does the things she does so far and what is happening now can give us better direction. We said before that she feels irrelevant because nothing she does independently moves the narrative. She's done things on her volition that plots where she goes from here.
You think Oda just brought a character along to do nothing but being a buffer to Chopper, or to hype Sulong, or to "give Chopper ideas for a powerup," or being fanservice? He overall keeps her in the story doing things because her was never clearly established. She's an independent variable doing her own thing until the story brings it to attention.
Also, Jinbe was first featured in Impel Down, participated in Marineford, and was on Amazon Lily helping Luffy recuperate. He was a side character in all those arcs, but he was a more prominent and significant side character. That's the difference.