FWIW, though I never heard of Macklers before, my son has ADHD yet my wife and I refused to give him meds, in spite of that causing us to have to let go several therapeutic teams, until we finally found one that accepted our decision. We figured exactly what you just said, that we must be the primary cause of his ADHD so that is were the solution must be found.
Having said that, his 12 now and I'm still struggling to let go of the bad parenting I brought him up with. Among many others, my most fundamental mistake was to think that not only he must obey my command as the father (which is wrong) but he also must want to do it (which is lunatic, no one really wants to do as told, even if I thought I did as a kid), which made me snap really badly each time he was defiant. That's how I was raised, and by my "dad" who was actually just the married lover of my mom, so he had his own real family and only came home occasionally on the weekends. But when we he did come home, we were like in the military. On the other hand (and this is the tricky part), he did love us, and what he did was that much harsh for our own good, so I always thought that was the way to do it.