I was wondering if Jinbe’s late addition to Straw Hat Pirates crew is not just strategic reason in terms of plot but also symbolic.
Luffy should always be the strongest Straw Hat being the leader. And as we know, Luffy has just learned how to use Advanced level of Armament Haki in Wano.
If Luffy hadn’t learn Advanced Armament yet and Jinbe joined before that, technically Jinbe would have been the strongest person in Straw Hats crew.
Now, that he has unlocked both Advanced Conqueror’s Haki and Gomu Gomu no Mi Awakening, Luffy is on a totally different power level than Jinbe and the other Straw Hats.
It should be noted that also Sanji and Zoro just got a power up, which can be said brought balance to add Jinbe to the Straw Hat Pirates crew.
Sanji was able to defeat Yonko Kaido’s second strongest Commander.
In his fight with Queen, Sanji awakened the same genetic enhancements as his siblings, gaining an Exoskeleton and superhuman physical constitution, including accelerated healing.
Sanji has become fast enough to the point where he seemed to vanish right in front of Queen right before attacking him and can seemingly turn invisible without his Raid Suit. As his enhancements were complete, Sanji has shown far greater power in his fighting style, able to knock down Queen with immense power and develops fighting techniques that would have been physically impossible for him to do before.
During the Wano Country Arc, Sanji revealed Ifrit Jambe, a new enhanced version of Diable Jambe. It is the result from the awakening of his genetic enhancements combined with his trained Busoshoku Haki increasing his leg’s strength and endurance. With this new technique, Sanji’s legs can withstand much hotter temperature and are thus capable of generating much stronger flames, a feat he would have been unable to achieve without his newfound powers.
Zoro unleashed Conqueror’s Haki. He strengthened his “Kyutoryu: Asura” using Armament and Conqueror’s Haki, which allowed him to leave a permanent scar on the “Strongest Creature” Kaido in his hybrid-dragon form.
Zoro was able to defeat Yonko Kaido’s 1st Commander King.
He awakened Advanced Conqueror’s Haki, was immediately able to use it to coat his attacks, figured out King’s power, and defeated him in three blows.