Do you think HCI is a science? If yes, do you think we can have a systematic and forever valid HCI theory in the end? If no, then what is HCI, and what is our position as HCI practitioners?
I believe you are suffering from what is called "category error." No profession is a science. Practitioners are not scientists and it is a mistake to pretend to be one. Similarly, scientists are miserable practitioners. These are different categories.
Look at medicine, law, civil engineering. and programming to take four simple examples. Most professions are based upon science, but they are engineering, which means much of what they do is still an art form. Civil engineering is a good example. Bridges fail. Dams break. Programming errors proliferate -- software is buggy, malformed. This is to be expected when the pure dictates of a science are applied to the real, messy, unpredictable world. This is why we need consultants and Gurus. Biology and mathematics do not need consultants. Medicine and economics do. So too with programming, bridge design and construction, and the applied world of HCI.