ADHD is frequently hereditary, and substance abuse and addiction are common for people with undiagnosed ADHD.
Your own story of dropping out and teaching yourself isn’t just familiar to me, it’s similar to both my brothers’ stories as well.
I’m sorry you experienced this the way you did. I wish you had better medical care, and better parental guidance. I hope the life that you’ve made for yourself is joyful and prosperous, and I hope if it’s ever not you’ll find your way to that however it makes sense.
Does my brain work differently than other people? Yes. Would this have been a problem for me in any pre-industrial society? (Which, to be clear, is most of human history?) I don't think so. Is it a problem for me when I have a fair bit of control over the work I do? Not really! I only experience it as a problem when I am expected to function in contexts with industrial-age labor models, where there's a hierarchy that expects me to labor like a robot in line with how my betters have decided how the work should be done.
So I can entirely believe that authority figures over-use ADHD as a diagnosis so that their lives are easy. Reading through the DSM, it seems to me there are quite a number of diagnoses that could be used as Authority Inconvenience Syndrome. And I don't think I've ever seen one where people might need treatment for being too obedient.
It is quite illogical but very popular because well adapted people can just talk about superior genes and how everyone else has inferior genes and they can never change anything about that except with extensive medical treatment.
I dropped out at 15 and taught myself computer science, so it was all provably horseshit but it sure made my life harder as a child.