Gabor Mate is full of shit about ADHD. He's put no evidence forward for his claims at all other than his own experience. But he does have some helpful strategies to offer families, that I will give him. And he's bang on the money with addiction, where he has done most of his actual research.
What research does tell us is that ADHD and autistic individuals are more likely to also be traumatised, experience ACEs, and experience social and economic exclusion, so even trying to separate them out diagnostically is hugely difficult. When I did assessments, we would usually take the line of working first on any suspected trauma based presentation and if that improved with therapy and parenting changes, then diagnostic criteria were unlikely to be met for ADHD and/or autism. But where challenges persisted, we would need to think again about reassessment.
Neurodivergent is an identity based term, not a diagnosis, so of course if people expect it to have set criteria like diagnosis does, they will find it vague. It isn't meant to substitute for diagnosis.
Where we can agree here is that there are certainly aspects of modern life and modern parenting that are likely to exacerbate the more distressing aspects of neurodivergence. It's unpopular, but too much screen time, if you have a child prone to issues with attention regulation, isn't good. Ditto a carb and sugar laden diet. Not enough time being physically active and outside. Same for lack of structure and a chaotic environment at home. This one is tough, because you're often working with ND parenrs who struggle with those things themselves. So they need support first to be able to support their kids. And compassion, because we have all been over here masking and white knuckling our way through without knowing there were other ways. (I was one of those struggling adults before my DC were assessed and the penny dropped - even as a psychologist, I didn't see it).
The whole "is it ADHD/autism or trauma" debate is bullshit and a red herring, because we nearly always have to think "both/and". People don't fit neatly into boxes that way.