Incidentally, I think this is the strongest argument against Egan's General Intelligence Theorem (or, alternatively, Deutsch's "Universal Explainer" argument from The Beginning of Infinity). Yes, humans could in theory come up with arbitrarily complex causal models, and that's sufficient to understand an arbitrarily complex causal system, but in practice, unaided humans are limited to rather simple models. Yes, we're very good at making use of aids (I'm reminded of how much writing helps thinking whenever I try to do a complicated calculation in my head), but those limitations represent a plausible way for meaningful superhuman intelligence to be possible.