Prior to 2001, it was not against MLB rules to have or use performance enhancing drugs.
2001 MLB enacts drug testing in the Minor Leagues.
2003 Drug Testing begins at the MLB level as a "survey" phase. MLB later announces 5-7% of the 1,438 tests were positives. Later, 2004 results were announced as 1-2% positives.
2005 Alex Sanchez becomes first MLB Player suspended for PED.
This is like trying to determine if the Soviet athletes were clean during past Olympics. At one point, it wasn't necessarily prohibited.
Just because it wasn't prohibited, doesn't make it right. I will add, that I do not believe PED usage was greater than 10% of the players. In some cases, athletes use a cold medicine or anti-inflammation that contains a banned substance.
Weight training as a science is better than ever. At 52, I know more about building muscles than when I was at 18, 28 or 38. I weigh 40 pounds more than when I retired from the Army (2000), of which, 30 pounds are raw muscle weight.