@Ryuksgelus:
Jinbe has been dealing with them for a lot longer. G2 is Luffy's shortcut making up for his lack of combat experience.
Though I disliked Gear Second since it's introduction, I found it more acceptable when Luffy first used it to overcome the daunting threat CP9 represented. It promoted Luffy's unyielding strength of will, an act of pushing himself far beyond possible limits at the expense of his body. And at that time, as you point out, Luffy was still a new rookie, up against daunting adversaries whose prowess was well established in the One Piece universe. As we have moved on, however, I'm disappointed that Luffy, no longer a rookie considering his two years of personal tutelage from the late Pirate King's "Partner" himself under his belt, still relies on a shortcut for a boost beyond his natural physical ability: why is Luffy, the protagonist, the only one (beyond the New Fishman Pirates) who can't rely on his natural physical prowess?
Still, Gear Second would be more tolerable for me if Luffy's, the full-body brawler, natural physical ability matched his peers/opponents, and with Gear Second, he gained a notable physical superiority. That is to say, the fact that Luffy are able to utilize a physical boost shouldn't mean that his natural physique are lacking: that defeats the purpose of the power-up in the first place, and only makes Luffy look bad (i.e. he needs the boost just to physically keep up).
The problem is that the boost from the Gear Second (at least pre-TS) is far too big. For instance, against Marigold and Sandersonia, he went from being trounced in base to doing the trouncing himself with Gear Second. Therefor, if the magnitude of the boost remain unchanged, his physical edge would be too significant, if his natural physical prowess was comparable to his opponents/peers.
^That being said, though I'm currently pessimistic regarding Gear Second and it's significance, it's certainly possible that Oda will make it work out well enough. The best option I can see, aside from removing it completely, would be to substantially lessen the boost Gear Second provides.