Agenda aside I actually agree with you for once.
However, one has to understand that oda was trying to strike a balance here between Luffy and Zoro portrayal and Gaban portrayal to ensure no one gets de-hyped.
Gaban hasn't shown anything remarkable yet. His little feats mean nothing when Luffy was just casual.
Yet, there is element of good portrayal which oda touched - Luffy and Zoro both recognizing Gaban is real deal and were ready to tag team to fight him with Luffy even going Nika.
At same time, whatever Gaban did has no effect on Luffy's portrayal as well.