Sequences contain a rational world view. Not a comprehensive one, but still, it gives some idea about how to avoid thinking stupid and how to communicate with other people that are also trying to find out what's true and what's not. It gives you words by which you can refer to problems in your world view, meta-standards to evaluate whether whatever you're doing is working, etc. I think of it as an unofficial manual to my brain and the world that surrounds me. You can just go ahead and figure out yourself what works, without reading manuals, but reading a manual before you go makes you better prepared.
That's asserting the thing that the original question asked to examine: how do we know that this is a genuinely useful manual, rather than something that reads like the manual and makes you think "gosh, this is the manual!" but following it doesn't actually get you anywhere much? What would the world look like if it was? What would the world look like if it wasn't?
Note that there are plenty of books (particularly in the self-help field) that have been selected by the market for looking like the manual to life, at the expense of actually being the...
LW doesn't seem to have a discussion of the article Epiphany Addiction, by Chris at succeedsocially. First paragraph:
I like that article because it describes a dangerous failure mode of smart people. One example was the self-help blog of Phillip Eby (pjeby), where each new post seemed to bring new amazing insights, and after a while you became jaded. An even better, though controversial, example could be Eliezer's Sequences, if you view them as a series of epiphanies about AI research that didn't lead to much tangible progress. (Please don't make that statement the sole focus of discussion!)
The underlying problem seems to be that people get a rush of power from neat-sounding realizations, and mistake that feeling for actual power. I don't know any good remedy for that, but being aware of the problem could help.