It could be that people don't use their rationality skills at their "bottlenecks". You could improve many things but if they aren't your bottlenecks the result would be negligible. I've seen people training to recognize their biases but not using this for strategic planning and just doing "the safe thing" everyone does.
It seems like maybe what’s going on here is that the author of the linked post has come up with (what he considers to be) a fancy new kind of edutech, and in order to hype it up, he’s got this grandiose, sweeping thesis about how “books don’t work”, and his fancy new thing is the answer. Well, shiny modern edutech ideas are a dime a dozen. They’re mostly empty promises based on questionable theories. What makes this one different?
I don't want make any general statements. But in this particular case the spaced repetition algorithm is mentioned by the author. And there is pretty solid evidence that it works. Many studies show that it raises long-term retention.