g2 and g3 were not unlimited in their introduction but post time skip they became unlimited, so oda should have made g4 unlimited on the rooftop instead of making fluffy gas out that would have been perfect since he planned on introducing g5, unless oda never planned for g5.
I remember how Luffy fans were crushed by this when ch1003 came out and he gassed out... Ah the tears and cursing Oda...
Wrong expectations fellas, it will never be unlimited as long as haki is limited resource. In fact, I would argue that all gears are still limited, even 2 and 3.
Not that his performance would change with unlimited G4, it would only make him look worse. At least like this excuses are possible but if it were unlimited yall would simply have to accept that he is too weak.