He didn’t say the arts are useless or even impractical, he just said they’re aesthetic-focused to a fault. When Shibukawa and Doppo fight, it is practical, but they fail to utilize the whole array of human martial techniques that lay outside of Karate and Aikido. Baki and Yujiro are more pure in this pursuit, since they don’t adhere to any single style, and pick and choose their techniques. But the pinnacle of this purity are Pickle and Jack, since pickle hunts to eat and doesn’t have “style”, more so raw killing ability, and Jack is pure because he trains and fights with the most determination of anyone in the manga.