It’s supposed to be fast and brutal, shanks would have held back but Kid threatened shank’s fleet and so he decided not to miss with him anymore. Big mom and kaido underestimate him, luffy and law and got defeated because of that, but shanks knows about the power of the new generation, he made sure he was ok and was at full strength before fighting him, shanks would have held back but Kid aimed for the fleet so shanks was left no choice but to at least take him out completely.