Big Meme got blitzed by Brook, blocked by Chopper, sent like a cannonball by Jinbei, ranned over by Franky, etc, ect. While these things definitely makes Saturn look incompetent, it has little to do with his power level, but rather Loda solely writing events in ways they need to happen for the plot to move forward, logical or not. Same reason why Saturn kept taunting Bonney instead of simply popping her head like a grape.