Here's the deal with Big Mom. She is intentionally written as incompetent or put into scenarios that favor the protagonists, as a means to counterbalance the fact that she's a fucking Yonko, and if there wasn't some kind of medium in play, she would kill everyone on the spot, and the story would be over. You powerlevel junkies need to get that through your heads. One Piece isn't written through the perspective of strength. Oda needs to drive the narrative forward, not bring it to a screeching halt.