He's not wrong. Schools are day-prisons where parents leave their kids while they slave away to make the rich richer. Most teachers (in my experience at least) are absolute shit, and so are the education systems (again in my experience). And before the 'in the Scandinavian countries...' bunch comes: I know a few Nordic people, not impressed, they just have lots of money to throw at the problems (which I would say is the secret for every other statistics they excel in).
Quick edit: that being said I don't know anyone, including myself, that has learned a language with Duolingo. Can be fun but it's useless for actually learning.