An engaging teacher makes the effort worth it. So it doesn't feel like the contrast effort required if oriented horribly. I fully believe there are good teachers and bad teachers. But that's why I used the word biology: there is no way to learn without effort. Your relationship with the effort is the important point.

> Duolingo is just one example that there is plenty of money to be had even with dubious claims and a product that doesn't actually work that well.

That's my point, it doesn't actually work for learning. Duolingo sells feel-good vibes of being productive with your doomscrolling time. It's learning-porn basically (could be worse).

> Any for-profit initiative (ed-tech) will not be incentivized to improve learning outcomes. There's no money in it.

I think a point to keep in mind is that even if some team cracked the ed-tech challenge and created a software that was wildly effective at getting students to learn, it would actually still be very difficult to get public schools to actually adopt it, unless they have some incentives like it being heavily subsidized, or free. And even then, it might not be free forever. That's part of the reason why ed-tech (even when it is proven to work) doesn't really make money.

> Duolingo is just one example that there is plenty of money to be had even with dubious claims and a product that doesn't actually work that well.

No, Duolingo is an example that proves that there is plenty of money in taking a flawed-but-useful education tool, and making it much worse in specific, habit-forming ways. I don't know that it proves anything about the profitability of providing learning: merely about the profitability of providing the perception of learning / a habit-forming activity that you can persuade yourself is a virtue.

Perhaps showing people metrics derived from the "proved it with data", after each session, to provide the perception of progress even when the learning task is frustrating? Looking into gym psychology, rather than (video) game psychology, might help. You'd want to try to encourage intrinsic motivation, rather than extrinsic motivation, but I'm not aware of any research on how to do that.

> We've all had a super engaging teacher or task in which we learned quickly and efficiently without it feeling hard

Turns out that when you enjoy something, the same amount of effort doesn't feel so taxing! Who would have thought?