The only double standard is that football doesn't mind a reputation for doping, and athletics does.
The WADA's role on paper is to combat doping, but its real function is only to repair and enhance the reputations of sports that want to conceal their dope use. To do so, it need only catch a few people using older drugs, and occasional screw-ups like Gay and Powell. This makes everyone it doesn't catch look clean.
If on the other hand it were to go after all the dopers and catch them, the reputation of the sport would be destroyed, probably never to recover, and it would go into who-cares mode like football. Then WADA would be out of business.
What incentive do anti-dopers have to succeed when they'll be out of a job if they do? Obviously they know about all the newer drugs. With all the reduced bans they've handed out, they must have plenty of informants. But they won't do anything about it until they have to, by which time there will be even newer stuff. They are purposely refusing to catch up.