The rules change all the time. What is now considered legal or unlisted will be listed in the future as illegal. I think a lot of dominating athletes are helped by "enhancements" that have a legal loophole and they continue dominating for their entire careers, then those substances get banned later on, and some never get caught until they retire like Armstrong.
The case with Armstrong is entirely different,he was doing these sort of things on a different level,he used to replace his entire blood and replace it with fresh blood and those of sophisticated methods were used by him to avoid getting caught and it is another level of malpractice,the loopholes are closing down and Olympic level testing could catch everything.