If athletes are getting away with doping, we shouldn't throw in the towel and just permit performance enhancing drugs in sports. A far better response would be to invest more resources into policing to help governing bodies get ahead.
The police play a game of cat and mouse with drug dealers, but they don't just accept their limitations and legalize all drugs. They invest more, develop new policing strategies and try to get ahead of the dealers. The same should apply to doping in sport.