Yes and Luffy's legacy is the people who follow him, Joyboy/Nika and fight for his cause. Dragon, who is Luffy's father, an Ex-Marine (maybe peer/ex-friend to Akainu? and wants to take down the Celestials, while realizing that 1) Imu is out of scope and 2) Akainu is their main weapon, might as well take him on (I'm not mentioning Sabo here so you don't cope too much).
While Luffy and Akainu can have a scuffle, it doesn't mean Luffy has to take Akainu down in a 1 on 1. Because Akainu is irrelevant in the grand scheme of things, unless he decides to have his own agenda and betray the WG.