I'm pretty sure that if ADD was a popular diagnosis when I was a kid I would have been diagnosed. My brain constantly pulls in multiple directions at once. I read (the operation) at a very high level since about age 5, but dont comprehend what I read. I like to read. By the time I complete a book, I've probably read it 4 times. Same with movies. I have to watch them a bunch to fully understand what is going on. Sometimes I cant even keep the characters straight.
I get bored with things easily unless it is mentally stimulating. When I was a kid, I would get bored with video games so I would play them upside down to make them fun again.
When I play the drums, I also sing and watch tv. Obviously I cant hear the tv, but I still watch it. My brain is also thinking about other stuff.
Ever drive and get lost in thought, only to realize you are stopped at a light, already made a turn, and had to stop at a stop sign also? My whole life is like this if what i am doing is just an auto pilot operation. I can mop the floor and not remember doing it, stuff like that.
If the thing i am doing requires my complete attention, like using a table saw, my focus is hyper vigilant. The problem then is my mind becomes exhausted and I need to do something else.
I was born mid 70s, before YouTube. So no, I dont think it is YouTube's fault. I think the lack of attention from parents allowing their kids to do whatever they want allows kids to be lazy, watch videos all day, not exercise, and become fat. When you are fat and lazy, you don't want to exercise. You want to continue sitting down, eating, and watching videos. Everything else just sucks because it isnt what you want to do, and since you havent been disciplined to do so, you really dont bother to even try.
My parents recognized that I needed constant mental stimulation. They did a wonderful job of making sure I always had things to do that occupied my brain. Some of them I still do, like puzzles. The more difficult, the better.