Psychology certainly seems to be a crossroads at the moment, and needs to do a bit of soul-searching to decide what it actually is, and what it wants to be. And in particular it needs to consider whether it actually wants to be a science, or something else.
Science is not the be all and end all of human understanding and enterprise. Indeed, I think the fact that psychology often does not meet the criteria for being a science is part of its virtue: great novels and literature are not science either, but that does not mean you cannot learn a great deal about human existence, life, and your own inner self from reading good novels.
Religions are not a science either, but nevertheless provide guidance (eg, moral, emotional and spiritual) on how to live life and how to behave and how to treat others.
The difference between science and religion is that the former is descriptive and the latter prescriptive. Science always describes what is, but human beings require more than that: we need to know what should be, and that's when the prescriptive function of religions, as well as the prescriptive function of our parents' instruction, the culture of the nation we were born in, or any other value system we may be exposed to, comes into play.
If you read the personality theorists — Freud, Jung, Rogers, Maslow, Eysenck, etc — their writing and observations on the human psyche are as much prescriptive as they are descriptive. Like great novels and literature, there is an essence of human truth to be found within the writings of the personality theorists, but you would not really call these personality theories precise science, just as you would not call Shakespeare precise science.
I don't think anyone would complain about the prescriptive role psychology takes; indeed, this may be considered as a valuable contribution to society. And I don't think anyone would complain when some areas of psychology try to follow as best they can the scientific method.
But the issue is the problem that Prof David F Marks is highlighting: where psychology comes face to face with biomedical science. In terms of trying to understand the causes of serious mental health conditions such as schizophrenia, or in terms of trying understand the causes of MUS diseases like ME/CFS, I think psychology must yield to biomedical science, which is a much harder science and has an increasing array of technological tools which will enable it to eventually get to the root cause of these diseases.
Biomedical science must be given priority and primacy when it comes to researching MUS diseases, as well as serious mental health conditions (which increasing evidence suggests are organic biologically caused illnesses).