Pica in his Golem form could not harm any of the gladiators that were with Luffy, only the statists, the environment(houses and buildings). Against strong opponents, he is not a rival, he can only delay time. But I understand that some type of people are very impressionable to demonstrate something large-scale.
[automerge]1582460213[/automerge]
Pica needs time and concentration on the part of the body that he wants to restore. While he was restoring his arm, Luffy managed to activate 3 gears, jump up to his head, and destroy it. Cracker probably would not have to personally join the battle, would create a cracker bots and start systematically destroying the Golem, starting with the feet, because it's just a stone, though alive.