> can't fit all the "knowledge" out there

We don't know that. Given how environmental factors fuck up plenty of neutral layers and synaptic graphs, there is reason to believe that if we stopped or reversed that, human brains might be able to fit all the knowledge out there, given enough time. The constraint then would be preference. Because let's be honest, you wouldn't give a fuck about the Kardashians and the history of their influence on markets and teen desires in America.