I am not relying on my "perception of the experiences of athletes and coaches", as you describe it; I am observing the undeniable fact that doping is endemic at the highest level in the sport, and it is beyond credulity to suggest this will not be a significant factor in performances. However you try to argue it, irrationality is not what drives athletes' decisions to dope - with you as the lone voice for rationality. Athletes don't dope as a one-off speculative experiment; it is typically a programme, which few would continue with if it did not produce results. The experiences of other athletes would reinforce those perceptions. As the baseball player Jose Canseco said in his autobiography, "Juiced", everybody doped - because they knew what it did for their game.
As far as Renato's experiences are concerned, it has been pointed out that none of his athletes (bar one, in the 3k steeple) is a world record-holder in any of the major track events, middle or long-distance. Nor are his athletes amongst the current top performers in those events. It can only be assumed that the present world track records are clean, but if they are not then the best clean performances by his athletes are not as good as the very best performances, clean or doped.
I further point out the obvious, that his conviction that training is superior to doping is formed, firstly, without experience of what doping might do for his athletes, and, secondly, is not shared by the thousands of athletes convinced that doping helps more than training alone. The question he hasn't addressed is whether doping could add improvements to his athletes, above and beyond the training he provides. How would he know the answer to that unless he and his athletes tried it? His view of the relative merits or otherwise of doping therefore remains speculative - and, in your favoured words, is "confounded" by the experiences of the many athletes who have doped for generations.