Or, at the very beginning of when evolution reached a "high enough" intelligence to make us use tools (to make tools), it ceased to be of significance compared

Or, at the very beginning of when evolution reached a "high enough" intelligence to make us use tools (to make tools), it ceased to be of significance compared to the rate of civilization evolution we experienced. We domesticated fire 400,000 years ago, I don't think human level intelligence hasn't evolved much since. (Nutrition, education, knowledge sharing increased much though!) So, our current brain architecture is "one" reached solution (not an optimal) in the possible states of evolved intelligences. Also, our brains are not under-utilized. We don't really know how everything works, and for startes our brains are very robust!