But there's a difference between overwhelming power, and just looking like losers. Luffy is apparently the only Zoan in the world with a ridiculous stamina drawback, Zoro's win over Lucci has to have Jimbei show up, Robin was apparently defeated offscreen, and they could only save one Vegapunk.
And now we have Imu here, so the odds of Luffy defeating him, even though an avatar, when he actually couldn't hurt a Gorosei, is highly unlikely.
So, we have two back to back arcs of our supposed heroes looking like jokes thanks to stupid magic bullshit. What fun!