it's a disorder when it effects how you function and how happy you are with your life. if you can live a happy life without medication, and neurotransmitter deficiencies, kudos.
some people with physical deficiencies have no issue navigating the world, and some do. same with queer folk. same with people with ADHD. sure there's a societal aspect, but there's also relationship aspects and everything else. we don't live in a vacuum. you can't look at it from the perspective of "if we were hunter-gatherers we would be fine" because that's not the reality of the world.
and fwiw there are plenty of things one can do that are not working 8 hours a day, that are not working during 9-5, that are not focus related. you just choose not to do them, or do not find the proper opportunity.
and that's why medication exists. so people _can_ do normal things and live a normal life. the system isn't great, to be fair, and i wish it were reformed, but until the glorious proletariat uprising, i'd prefer people get the mental health they need to focus on their lives and not some fictitious idea of what may be