The sequences require a strong base to read/understand and a lot of endurance
I won't argue with endurance, but what do you mean with "strong base"? Where in the sequences are you expected to already know something that's not part of the sequences? I've read most of it (didn't care to learn about quantum physics) and don't remember such a thing.
I don't know math, quantum mechanics or philosophy, i had to open 10-20 pages of references and google searches to follow what was going on(per individual sequence page).
It reads as though it is assumed that you are a AI graduate.
Its also strongly aimed/influenced by american culture, so some things are weird for us Europeans.
Iksorod and I made a Google doc of intro-level training materials for rationality / critical thinking. We'll keep adding to it as we find more stuff. Please comment with your own additions.