Thing is, Luffy always lost his battles if not to outside's interference. Was, is, and maybe always will be.
That's different from the other Monster Trio's battles.
Did Zoro get help from outside when he fought King? Nope. Yes, he won with power up but he never got any help from outside.
And yes, there were 2 outside interferences, but both of them were disadvantages for him: Enma and Sanji calling like a dumbass.
Then, did Jinbe get help from outside when he fought Who's Who? Nope, he won clean, stomped the opponent, not going all out, not needing any power up, and he won without water.
Meanwhile Luffy? He always lost if not to outside's help.
Drowned to death against Arlong if not saved by villagers and Sanji.
Lost to Crocodile if not saved by Robin.
Lost to Rob Lucci if not interfered by Usopp's distraction.
Lost to Doffy if not saved by gladiators.
Lost to Cracker if not helped by Nami.
Lost to Katakuri if not saved by Brulee.
Lost to Kaido if not saved by Law's crewmates (let's forget the Rooftop to not embarass him further).