You can design something to be 100% usable and logical to your end-user, but if the product is dull-as-dishwater people may still have no interest in using it.
The UX-factor: why I don’t care where or what you studied
Bram Bos
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My company appears to be going into the opposite direction: we are producing more “pretty” and “aesthetically-pleasing” designs (subjective), vs. usable and logical to our end-users. We have lost several of our human factors/cognitive psych senior members w/10+ years of experience and are replacing them with junior designers, who have no experience in HCI, UCD, and no mentoring.

So while I agree with the notion of varied backgrounds — I, myself, with a CS background who has the passion, empathy, and knack for problem-solving, who was mentored by those with the HCI background — I think the base has to still be knowledge of human factors and usability. (Note: I don’t think that this article is saying otherwise; just wanted to mention another case. :))