I’ll add my anecdote; since the OP is looking for opinions, I hope it’s valid.
I was a great student pretty much up until high school, when I stopped caring about a lot of things and realized I could still get solid grades without putting forth a lick of effort. I think I graduated with something around a 3.5 GPA. I got into a honors engineering program at a good state school, and promptly got my ass kicked. The combination of real courses requiring real effort, plus ample access to alcohol, video games, and women, meant my grades plummeted and I fell into a spiral of depression that caused me to blow off class more often than not.
On my way downhill my parents, understandably concerned, convinced me to seek mental help. My mom made all the appointments, I just showed up and did my best to be honest. After less than an hour with a psychologist and another 45 minutes or so with her ex-husband the psychiatrist, I was diagnosed with ADD and depression, and given scrips for Adderall and Prozac.
I hated both drugs. The Adderall made me anxious and would make my heart race, so I stopped taking it after a week. The Prozac made me listless and destroyed my libido, but I lasted a couple of months.
Ultimately I dropped out, got my shit together, got a degree in a subject I could handle (unmedicated), and have gone on to live a model life. I’ll readily admit that the depression was real, if not caused completely by my environment, but the ADD was completely bogus. I couldn’t concentrate at the time because honors chemistry is feckin impossible to concentrate on for a 19 year old who just wants to chase tail. And the thing is, if someone had said to me, “Maybe computer engineering is too heady for you, why don’t you just get a generic CS degree?” I would have graduated on time and nobody would have ever accused me of having a mental illness.
So to the OP, there’s where my skepticism of AD(H)D comes from. What I learned back then was that you can be smart, like really smart, and still be better suited to a blue collar job. I think I’d be happier as a mechanic, honestly, but the track I was on tried to shoehorn me into a life I wasn’t ready for. And when I failed, instead of anyone admitting that maybe I just wasn’t as good as I thought I was, they readily accepted that I had a mental illness. That’s just bonkers. And the shitty thing is, my diagnosis was a slap in the face to kids who are actually struggling.
I have no doubt that there are D and F students who can benefit from medication and/or a proper diagnosis, but any problem I had with concentration had no major impact on my ability to lead a normal, even successful life. So, count me among the over-diagnosed.