As prase said, you've been confused by the specific term used - the "Traditional Rationality" that EY was talking about isn't the actual human being that was Karl Popper, but the pop-culture version of Popper which has been a major influence on the thinking of most scientifically-literate people of the modern era.
To make an analogy: if someone asked me what "Romeo" and "Juliet" meant in Taylor Swift's song "Love Story", my answer would be quite inaccurate as a description of the play - because the "Romeo" and "Juliet" in the song aren't the two love-besotted idiots in the play, they're the stereotypical young lovers of pop culture.
You say Eliezer is just talking about the pop-culture version of Popper, rather than actual Popperian philosophy. So he knows the difference right? He knows that pop-culture contains a lot of myths about Popper right? I don't think so. Eliezer's criticisms are actually directed at Popper, but he doesn't understand Popper, only some pop-culture version.
Here is an example from my wild and reckless youth:
...The way Traditional Rationality is designed, it would have been acceptable for me to spend 30 years on my silly idea, so long as I succeeded in falsifyin
In several places in the sequences, Eliezer writes condescendingly about "Traditional Rationality". The impression given is that Traditional Rationality was OK in its day, but that today we have better varieties of rationality available.
That is fine, except that it is unclear to me just what the traditional kind of rationality included, and it is also unclear just what it failed to include. In one essay, Eliezer seems to be saying that Traditional Rationality was too concerned with process, whereas it should have been concerned with winning. In other passages, it seems that the missing ingredient in the traditional version was Bayesianism (a la Jaynes). Or sometimes, the missing ingredient seems to be an understanding of biases (a la Kahneman and Tversky).
In this essay, Eliezer laments that being a traditional rationalist was not enough to keep him from devising a Mysterious Answer to a mysterious question. That puzzles me because I would have thought that traditional ideas from Peirce, Popper, and Korzybski would have been sufficient to avoid that error. So apparently I fail to understand either what a Mysterious Answer is or just how weak the traditional form of rationality actually is.
Can anyone help to clarify this? By "Traditional Rationality", does Eliezer mean to designate a particular collection of ideas, or does he use it more loosely to indicate any thinking that is not quite up to his level?