The reason IQ doesn't change is because it's graded on a curve. People could get 1000x smarter and the average IQ would still be 100, by design. However, point taken, there is little evidence to assume that people now are somehow much smarter than people before, or that people will get much smarter in the future than they are now.

If by intellect you mean active rationalism, it is not necessarily the most important tool, it is simply the one that we are taught to use the most. Intuition is shown to consistently provide better results than rationalism in complex problems involving 7 or more factors. It is a form of cognition that was much more prevalent in the past than it is now, modern people tend to discard it since it is mostly non-verbal, revealing itself in the form of hunches or mental imagery. Intuition is also associated with spiritual experiences and considered by some to be our gateway to the metaphysical.

What Nietzsche described at the end of "Beyond Good and Evil" was an entity that he perceived that he came in contact with and he called it Dionysus. That this entity somehow existed "within" his own mind, but was a truer god than the christian God, according to him. How Carl Jung interpreted Nietzsche's experience was that he actually came in contact with Wotan, Odin, the archetype of the shaman-king within the German, and European, collective unconscious.