So luffy gonny revive big mom and beat her?
Using a "Luffy just says things" argument to reject something happening in the chapter is pointless. Using that logic Luffy shouldn't have fought Kaido, Kizaru, or anyone.
He said that line for a reason, and with Luffy and Loki moving on to Imu, someone needs to fight Sommers.
Oda's at least made Zoro somewhat involved with Sommers by protecting the kids from the thorns.
In comparison, Oda's kept Sanji completely separate. He's not even angry that Robin was captured by thorns this chapter. Didn't have Sanji go save the kids either. He's on the other side of the island too where Killingham is.
At least right now it makes more sense for Zoro vs Sommers than Sanji vs Sommers.