I hear what you're saying.
But it is the futility of doping.
No sporting achievement can be objectively assessed because, if all riders are doping, then the discussion degenerates in to "well, if rider B had access to the same dope/type of dope/medical sport/another, as rider A, B would beat A".
So not only does doping corrode the credibility of a sport - even when widespread doping is acknowledged in the sport, the argument changes to the merits of respective doping systems, in order to validate who wins.