I don't think Luffy is weaker than Gaban, but it's kind of hard to use anything from this chapter to argue that. He's teaming up with Loki, it's not really shocking they'd be achieving more together than Gaban was individually
And using Gaban telling the Strawhats to run shouldn't be used in any serious powerscaling, that's just generic shonen writing. Ace isn't stronger than Marco and Whitebeard because Ace didn't wanna run from Akainu lol