Oda is a very predictable writer
With G5 Luffy is looking unbeatable and the fans are overhyping him like it was the case with the previous gear
Gear 2 and Gear 3 showed their limit in Thriller Bark, as Luffy needed the shadows to go Nightmare Luffy against Oars and to combine both to beat Moria
G4 showed his limits in WCI, as Luffy needed Nami's help against Cracker and to unlock FS against Katakuri
It will be shown by the end of the arc that G5 is NOT invincible, whether it is by Saturn or Kizaru hands.
Wouldn't even be surprised if Oda had this Luffy vs Lucci clash so he could show Luffy being overwhelming G5 one last time. Just to make the shock value of him getting packed in G5 even bigger.