One line that stuck out for me: "To the best of our scientific knowledge, human life has no meaning."
Maybe the meaning of life should be to improve our scientific knowledge. By understanding more deeply the nature, the universe that we live in and how the brain works, we could answer better this question.
Is not the problem misdiagnoses? There are a lot of conditions that mimic ADHD, I think the problem is that a lot of diagnosis are not thorough enough.
In the ted talk, he doesn't explain why this is not just a correlation. Maybe there is something else that makes you happy and makes one better at having relationships. For exemple, someone who has anxiety disorder will not be good with relationships and most probably will be unhappy. But the root cause of unhappines is anxiety.
I think what you are missing is the fact that this time the changes will take place much faster. With farming, the changes were slower and generational.(The children of farmers didn't do farming). And still these changes had colossal impact on societies(and a lot of blood was spilled).
And Terrence Tao who is quated was also extremely good at olympiads. As I see it, the olympiads are a good cost-effective way of identifying talented kids, they are in a way just IQ tests.
I think what you call it is more complex. As I can see there are three important capacitities: attention to details, working memory and iq (capacity to see patterns, what is tested in iq tests). In my experience they are all important, I'm pretty bad at the first two, and this makes me miserable in my job.
One more thing is emotional health, it's already pretty known that exercise helps with anxiety and depression. But I disagree about your assertion about intelligence, I think it plays a huge role in academic success.
Did you at least read the article ? He writes about replacing the current welfare system with UBI.
About the taxes, I think you are wrong because you think in black and white. It's not binary, it's a spectrum and you want to have a balance, in USA the current system is very favorable to the rich.