I think the author also ignores the advances of material science. Why just decide between hard and soft materials? What about a material that's soft at normal m

I think the author also ignores the advances of material science. Why just decide between hard and soft materials? What about a material that's soft at normal movement speeds but turns hard at the speeds of a bullet? Would solve the problem of being so restricted in armour yet it would look different. For sci-fi this is not unthinkable. There's already materials that harden under electric charge.