The one that seems a bit borderline but perhaps small enough effect and also already so commonly used by the general population anyways that its not too reasonable to consider it to be "doping" which would be caffeine.

But at that level, everyone is operating under the same rules. That's just the nature of competition, no? People will take any edge they can while following the letter of the law, if not the spirit.

Hell, even in the context of "on their own, unassisted", some countries directly support their Olympic athletes in terms of training, coaching and facilities, while other athletes have to pay out of pocket for that sort of thing and figure it out on their own and thus are more "unassisted", but there are no rules about that...

At the end of the day, all you can hope for is that the rules are applied justly & transparently.

yep, it is all individual. Some people have nice biology, some will get nowhere without "stuff". A recent blood test showed some anemia (that explained why i had such low level fatigue and tiredness threshold in the recent times, and you couldn't just make through it on pure will because it is like an engine with closed air intake - no oxygen, no burning) Started to take B12 and iron - things improved remarkably, physically and mentally. If i were a competitive athlete should i be forbidden from such a "cheating" way of increasing of blood oxygen carrying capability?

My understanding they ban testosterone which also increase the blood oxygen carrying capability. Which means that you're lucky to be born with high testosterone, and you're doomed otherwise (like me - i'm on a lower side). How is that a level playing field then? No exercise can compensate if you get less oxygen.

This is because there's not a lot of money in telling people to lift heavy stuff that's literally all around us and eat commonly available protein-rich foods. What is there to sell? In comes the gadgets and supplements.