I was assuming you meant epistemic rationality. I certainly believe creativity is great and an instrumentally rational goal.

My guess is that creativity has something to do with a feeling that some passing thought is interesting enough to be worth pursuing, but that doesn't mean I know whether everyone has enough passing thoughts to pursue.

I dunno if there is anyway to improve the generation of thoughts, save good genes and around 10000 hours of practice.

Having said that, slatestarcodex did have some interesting thoughts on how creativity might be simply the mind moving out of the ruts it creates for itself, the opposite of focus, explaining why creativity is sometimes associated with mental states such as being half asleep, on drugs or bipolar/schizophrenic etc.

As far as passion and interest goes, I suppose that this should come naturally with general good mental health.