Your lost hope is founded on this unfounded condition: "If it gives so much of an advantage ..." But what if it doesn't?
I haven't lost hope because I have looked for a long time for such evidence "at the top", and despite many allegations and accusations, I have found next to no evidence, for distance running events, and especially for men in the marathon, that "it give so much of an advantage". Not in 4 decades of doping performance research, and not in 4 decades of anecdotes of performances.
Although a lot of attention has been on Kenya in the last decade or so, doping has always been a worldwide problem. If doping really gave "so much of an advantage", we would have already long ago seen notable examples at the top worldwide, also outside of Kenya, outside of East Africa, and outside of North Africa, also from non-Africans. We would have seen it in the '90s, before worldwide standardization of anti-doping, and before testing could detect popular endurance doping with EPO and blood transfusions. We would have seen it in Russia in the 2000s, when they were doping all of their athletes.
But we didn't see any of that.
If you have lost hope, I fear you have done this to yourself, prematurely falling for the hype, both from people who don't know any better, and those who should know better.