"Play to earn" will never be popular, a large precentage of gamers are middle class people who absolutely don't need to collect pennies for hours of repetetive tasks.
As someone who played several games at the very competitive level (World of Warcraft) and games with complex economy (EVE Online) and made very decent amount of money with both of those, I say that you are wrong there. Anyway, time will tell regarding play to earn concept and in the end, play to earn is more than just some mindless grind for pennies.
And I also played a lot of games and were making money off them, and I still say that "play to earn" is unsustainable. When Diablo III was released, it featured real money auction house for all in-game items, and while some players made a lot of money from it, the majority of the community hated it and it was soon removed. Most of the gamers are not interested in making money from games, in fact they are very much against the trading of gameplay items - if you played WoW, you know how much the community hates gold sellers. Now imagine if Blizzard turned their WoW token into a blockchain token - now there's suddenly an extra huge incentive to run bots, scam people, hack accounts, etc. because there's an easy way to turn in-game money into real money.
AAA gaming industry is already making stupid money with their gambling mechanics and lazy-ass $60 releases and extra DLCs, whatever they can make with play-to-earn model just pales in comparison to that. But I believe this model isn't even profitable, because it pushes players away from the game.