If there isn't intelligence involved, then it definitely isn't designed. Or crafted, for that matter.

I suppose it could be perfect, by some particular criteria. But it seems unlikely. And in the case of the human brain, it's definitely untrue. The selection criteria for the human brain have been shifting wildly over the last few million years, so it's guaranteed not to be perfect.

Note, for example the long list of cognitive biases that we've so far discovered: https://en.wikipedia.org/wiki/List_of_cognitive_biases