@Sadistic Senpai I know it's a shonen but this series is ongoing for 20+ years yet Oda writes Luffy's character as if Sabaody never happened and all of the alliance members act like fucking happy go lucky they don't even take this seriously.
Luffy takes things less seriously because in his own eyes, the threat is LESS than what they encountered in Saboady...
By threat I do not mean Kaido is weaker than Kizaru
What I am saying is that for Luffy current level + his crew + the big alliance and strong members they have... according to what Luffy sees... it's NOT as threatening as having an admiral + shichibukai + pacifistas after them when they were weak back in Saboady..
For Luffy, he sees that the alliance has a chance of WINNING this war... which is why he can look chill and have som comedy scenes sometimes
During Saboady at that level... Luffy admitted that "we should separate and run, at our current state, WE CANNOT WIN"
so, the circumstances are different actually... because in Saboady, Luffy only saw an L coming down on them... while in here in Wano... he sees a chance of Winning and victory even if by our view, the audience, we feel the task is much more hard.. for the MC, he simply sees otherwise... which is what is causing that chill attitude from the crew