I didn't get that from the article at all.
He's not saying people don't have problems, he's saying the label ADHD is doing a disservice. It's not a condition, it's a symptom.
If we had a label called "breathing problems" and just lumped all lung-related stuff in there, it would be problematic too. That doesn't mean no one has lung problems, it means we need more narrow diagnosis such as pneumonia, cancer, cystic fibrosis, bronchitis, asthma, etc.
The article is completely right. Any disorder that fits 90%+ of the population is too broad. Either it needs to be split into multiple disorders or the criteria need to be tightened.
This is a categorization article, not a "there's no such thing as ADHD they're all faking it, work harder slackers" article.
But the article is potentially harmful because it discounts this population and pretends that there's nothing there. The author says "there is no such thing as ADHD" without allowing for the possibility that there actually is, but it's far too broadly applied and needs to be tightened up.
And as someone with ADHD I never hated taking the medication. It was, like for the OP, a great experience that let me do a lot of things I didn't think I was capable of doing.
I do hate taking too much of the medication, granted. Accidentally doubling my dose is always something that I really regret.
People will self-medicate when they can, and they will use anything that reduces the symptoms they perceive as problematic even when those substances have detrimental effects elsewhere in their lives. Taking into account only correlation, there are abnormally high numbers of people with chronic depression or dysthymia among alcoholics and those addicted to other CNS depressants (like barbiturates), of people with bipolar disorder among cocaine addicts, and of schizophrenics among people who even the most pro-weed activists would say use an, um, immoderate amount of hallucinogens.
So it is unsurprising that people who have something like ADHD (for want of a better label) may find relief for the symptoms they feel in some substance that at least gives them the perception that the problem is ameliorated (whether or not it actually helps functioning). And since the problem reduction is imperfect or short-lived, there is apt to be a bit of overuse or compensation for diminishing returns (rather like the "sunk cost" phenomenon). There is nothing to suggest that medications that actually work tend to be abused among that population (accidental missing or doubling notwithstanding - I do that with my Parkinson's meds occasionally, and it ain't fun when I do).
As a long-time recovered addict, I have no trouble saying this: the biggest problems with medications that you actually need is that they only do what they're supposed to do. (Post-surgery morphine was a complete bust, and it went away before I could rely on it for anything but high-level pain.)