Know that you are far from alone in this experience.I think I'm a pretty experienced gamer. I've played a lot of systems over the past 30 years or so: every version of D&D, Call of Cthulhu, Warhammer Fantasy, Savage Worlds, Shadowun (gulp!), GURPS, Year Zero, PbtA.
And wow is Runequest on the complex side.
The rulebook is laid out very bizarrely.
You start off with centuries of history, then learning about cults (which you swear loyalty to and are thereafter referred as symbols for the rest of the book). Then you choose what your character's ancestors were doing during various historical events. Then you roll stats and figure out derived stats by averaging different combinations of stats, which are modified by the ancestral events and your cult runes. Which you then need to figure out which of a few dozen skills are modified by which ability scores. And then you get modifications to those skills based on your culture, so on to this next chapter to see what those are.
I don't know how many chapters I'm in, and there hasn't really been a discussion of how die rolling works or the overall system.
It's a beautiful book, but I feel like the designers are trolling me with what might be the most convoluted presentation of any core rulebook I've seen in the modern era. I can't imagine anyone being able to use this as a reference book.
Call of Cthulhu has a simple, elegant, and (dare I say it) beautiful game design. What happened to Chaosium here? I can't read more than 10 minutes without completely losing track of what I'm looking at.
I love what I've read of the Runequest setting. The system? It took an effort of will to even temporarily comprehend it and it has since faded lol.