That being said, there is probably such thing as too much hidden complexity. If most of the information in a given society is hidden, embodied by non-human intelligences, then life as a garden-variety human would be awfully boring.

It sounds like the problem would be too little unhidden complexity. I don't see how adding a process that you don't know about could make anything more boring.

Considering that we're perfectly capable of making games with unhidden complexity, I don't forsee this being a problem.