It's ADHD when it affects the individual's ability to achieve their goals, otherwise, yes, it is just a normal state of being.
However this classification schema is not necessarily well abided. And so diagnostics can become an expedient.
What we end up with is a rather confusing dreck that is more consistent with art than it is a science - rightly so. However, scientific justification seems to be increasingly necessitous in academia and is permeating more and more into the commons. The consequence of this is a whole field of people who may well be great artists posing as rigid empiricists and this retards both the development of the art while complicating the science by shear bulk, and jointly discrediting it.
The healthy thing to do, I think, is just pointing out that everyone is peculiar, strange, twisted, traumatized and that's simply the human condition. There really isn't a great deal of normal when we consider the multidimensional nature of a person, and existence in even a single tail in some distribution can drastically alter one's inclinations and abilities or cast them deeply into stigma.
In turn I think we would then necessarily have to accept the cold hard fact that a society fit for the human can't be engineered with mechanical expectations, which is a great deal of where these disorders stem from in the first place, the abstraction of man into a mechanical unit, for the sake of expedience.
Blah blah, rambling. Sorry.