What does Gene mean by Phineas you wouldn't be any good in the war even if nothing had happened to your leg. What qualities make Finny a poor candidate for military service?

Gene is suggesting that Finny lacks the necessary qualities for military service, such as discipline, conformity, and competitiveness. Finny is carefree, nonchalant, and does not take things seriously, which are not traits conducive for success in a structured and disciplined environment like the military. Additionally, Finny's inability to see the harsh reality of war and his naivety towards the world make him ill-suited for the challenges and demands of military life.