The thing I learned, as someone who studies a hard science, is that a lot of "diagnoses" are arbitrarily defined with no known biological markers or laboratory tests to identify the condition.
Many such throwaway diagnoses exist in all specialisations of medicine- IBS in gastro, POTS in cardiology, fibromyalgia in rheumatology and ortho, depression/anxiety in psychiatry, chronic fatigue syndrome in immunology, etc. Basically, all of these are umbrella terms to mean, they have no idea what's actually wrong with you, but they can't deny that the pain you're experiencing is a tangible, real thing. (many doctors still do though)
Having such labels can be helpful if you need them to get disability benefits or adjustments at work/school, but can be the nail in your coffin if you seek advice for a different condition later, that gets conflated with your depression, fibromyalgia, anxiety, and so on.
I was misdiagnosed many years with anxiety, when I actually had ptsd and autism. Unfortunately, psychiatry doesn't really understand ptsd, so any sort of treatment you will be offered will be the exact same SSRI/SNRI bullshittery that doesn't touch the areas of the brain that are most effected by ptsd. I think ptsd should be studied from a neurology perspective and not a psychiatric one, so getting diagnosed by a psychiatrist didn't really make a difference for me because they weren't really sure how to help. Throw the same talk therapies and SSRIs and see if they stick was their penchant.
When it came to my other conditions, I pretty much had to figure out myself what was wrong after all my tests came back clean, as doctors tried to say, oh its just stress, or oh, we don't know. If you have an illness that is clear cut, say arthritis or something of that sort, getting a diagnosis will be beneficial to you. Getting a diagnosis for something that is not well understood and doctors are ignorant about, feels more like a death sentence.
