It's pretty cool that we know Luffy is kind of a simpleton, i.e. he has a one-track mind but that also plays in super well with his character normally because that's twice now that everyone else is kind of panicking about all the other problems to solve and he cuts to the heart of it by saying so basically I have to defeat the head honcho and we're good, right? It happened in Arabasta when Vivi wanted them all to go stop the rebellion and again now when everyone's talking about defeating shadows. Solid character consistency!