I really like the way you put it. In isolation, humans today have essentially the same natural mental capacity we had 2000 years ago, but we've become part of a much bigger computer. A human brain 2000 years ago was a very isolated entity. Even in centers of learning in the classical era, the amount of knowledge one could tap into was vanishingly small compared to our capabilities today. Everything and everyone was isolated in both space and time.
A brain today is not just an entity on it's own, it is intricately wired into the common consciousness. Crucially, we have a vast database of knowledge - easily searchable and distilled for maximum learning rate - all available at our fingertips. A modern brain is a neural network linked to billions of other neural networks, and all of them are linked to a shared memory that they can use at will.
Assuming that the main limiting factor is the bandwidth between a human brain and computers (and thus by extension between individual humans), then a direct interface could ostensibly bring about a new revolution (for better or worse).