Contador's epic ride on the Mortirolo wasn't even in the top 10 fastest climbs up it in Giro history.
How fast did Alberto Contador scale the Passo di Mortirolo? - Cycling Weekly
I'm not naive enough to claim that as evidence that he isn't on something, but it's clear that it's at the very least more realistic a possibility that a clean rider can compete today than he could have 20 years ago.