> very deep interests in things i was completely unaware that they existed ... say goodbye to the cognitive ability of a large chunk of future generations
I would think very deep interests in niche or obscure topics is correlated with increased cognitive ability, not a decrease.
> very deep interests in things i was completely unaware that they existed
That's just a symptom of getting old. Young people always find stuff that baffles adults. When I was a teenager, Anime itself was like this - just being "into" anime was considered some kind of bizarre, obscure affectation by adults.
I think smartphones present real challenges (and I don't get how/why they're allowed in schools), but a lot of what you're describing is normal.
anime waifus?