Do you remember MF? Most peoe didn't beat each other. They just hot somebody once and next chapter they fighting someone else. In a war you not going to get to finish off people when alot of things going on.
In the end to arrive above they need to take on Big mom,King and Queen.
The alliance will have a hard way, im sure Big mom will get out by a plot for shorttime so Luffy and co can arrive above, well King and Queen fighting off Sanji and Zoro.