In general I agree with you, but a counterexample to our rejection of their supposed heroism (and ascription of it to brain-chemistry-seeking identical to heroin addiction) is Alex Honnold [0], famous for his free solo of El Capitan in Yosemite. There's an excellent documentary on him, Free Solo [1], where it's very clear that he's neuro-diverse and that extreme climbing efforts put him into the zone, calming and focussing him. There's zero machismo to it. For him, it's an act of supreme, extended concentration.
I suppose in some sense it's still just manipulating one's own brain chemistry, but it seems a very distinct kind from adrenaline junkies.
[0] https://en.wikipedia.org/wiki/Alex_Honnold [1] https://en.wikipedia.org/wiki/Free_Solo
I do tend to agree that Honnold is an exception to the "why don't they just do drugs" argument. He's teaching us that we can do things we didn't think we could do, and I have to believe there's real value there. He's genuinely inspirational.
Climbing some random mountain in Russia, though... that's not "Holy fuck, what's this guy made of?!" but "Yeah, a bunch of other people already did that, and it was cool, I guess, except for the ones that died."
You didn't say it outright so this is not me correcting you specifically, but there's this semi-myth that "Honnold doesn't feel fear because that region of his brain is smaller than everyone else's". He, at least, disputes this. He feels fear but he knows how to focus it, and it's a combination of some kind of innate talent and conditioning as he's put himself in scary situations before
Not quite the same, but Youtuber Ally Law (known for climbing cranes and tall structures) started doing it specifically because he used to be terrified of heights and now seems to not have a problem with it