Did you read to the end? That's the idea he ends up with: only use nuclear propulsion for space-to-space travel where you don't care as much about shielding.
> If we need the full performance advantage of nuclear propulsion, we should design a spaceship that is intended for it from the get-go. It never lands, only going from orbit to orbit, so there is no need for heat shielding, flaps, high thrust engines, thick steel structure or aerodynamic shaping requirements.