Ok, I've actually debated with myself whether to post a comment on this question or not. There is a lot to unpack on this question, and as a matter of fact, Lemmy might not be the most appropriate space to talk about such a complex topic at length. I will try my best to answer in a balanced and rational manner. I'm a psychologist, have read all those experiments and papers, and I can say that maybe there are other points of view and deeper understanding you can approach from on these topics before casting such a wide negative opinion on a whole field of science.

Just to point something out of the gate, psychology is indeed one of the most misrepresented sciences in popular science communication. It is very difficult to explain in lay terms that what we know, experimentally, is from a really recent and young science. Psychology only really took off at the turn of the twentieth century, and just like most sciences, we have changed so much in the past 20 years alone that the public has had a very hard time keeping up with what happens in academia. If you were to scrutinize chemistry back when psychology was barely making its first steps, from today's perspective, you would think they were all wackos. We didn't even had a coherent model of the atom, radiation wasn't even known as a phenomenon and Pluto hadn't been dreamed, much less observed by the human eye. Look at medicine in the 19th century and by today's standard they were all butchers. But the point is that, they weren't malicious. Scientists were still trying to act in good faith with the limited knowledge available at the time, while still trying to expand said knowledge.

As a result, someone like Simon Whistle—who is not a psychologist but educated in business and law, and just a comedy media communicator—is probably working entirely on popular science's musings of already old science papers. Because that's what science does. We change what we affirm to be, probably, the truth as new experiences, ideas and theories are accrued in the collective understanding of reality. So, are there things that psychologist has been wrong about? Yes, absolutely. That's what science is. But changing the general masses ideas about it is an entirely different matter, and it goes at its own rhythm and speed.

One of the barriers is that psychology and human behavior and conscious, as well as subconscious thought, are things everyone has their own experiences and opinions about. Thus processing scientific experiences that clash or contradict an individual's anecdotal observations is challenging. Because, as with any science, nothing can be entirely deterministically predicted. Even physics, which we understand rather well, still has a margin of error and wide possibility for failure on predictions. Reality is simply too complex and has way too many variables for any single event to be predicted with absolute certainty. So, you will find experiences that seem to contradict scientific knowledge from psychology. But the truth is there are actually very few formal scientific laws in psychology.

Just to address your example, there is no prisoner's dilemma rule. It is not even from psychology. It is a game theory thought experiment. As such, it doesn't actually predict at all what people are going to do if placed on such circumstance, it's just an exercise to reason about what would a rational person do on different circumstances. By definition, on a formal prisoner's dilemma, the prisoners are defined to be guilty of some crime. So, I really doubt you were put in a prisoner's dilemma by the cops.

Just to reiterate. No, psychology is not littered with false rules and expectations. The public's perception about psychology is, indeed, littered with misrepresentations that claim that psychology has rules and expectations. Trust me, we don't have none of those you claim that are rules.

Finally, as for diagnosis. There is no per country definitions of mental illness. There are two comprehensive bodies of diagnosis. One is the ICD (International Classification of Diseases) managed by the WHO (World Health Organization) that standardizes and defines criteria for all medical diagnosis internationally. Including neurological, and psychiatric illnesses. Then there's the DSM (Diagnostic and Statistical Manual of Mental Disorders) managed by the APA (American Psychiatric Association) that standardizes diagnosis criteria of only mental disorders that was, until recently, a US only academic endeavor. There is overlap, which may cause this confusion that you seem to have. But they have radically different purposes and uses. Mainly, the DSM does a greater effort to contain psychiatric specific information regarding mental disorders that are not and probably will never be part of the ICD. While the ICD is far more international, comprehensive and integrated standard.

But that said, diagnosis is a very personal thing, think back about the confusion the public had about COVID during the pandemic when we knew so little. Even something as common as the influenza, every person manifest and experiences wildly different levels of severity and combinations of symptoms. For a myriad of variables, factors and reasons, some people die of the flu, some people have a mild nose discomfort for a while and are never aware that they were infected. This is the challenge that doctors, psychologists and psychiatrists face every day. As a teacher of mine liked to say, “the difference between your anecdotal experience and science, is that your anecdotal experience gives you one data point, a scientists ideally works with millions of data points”. You had your one anecdote, a doctor (or any other science based health worker) sees the experience of thousands of patients, and would have read about millions of other's experiences just by the time they finish their basic education.