Someone not too long ago linked me to research saying self diagnosis at least for autism is, in adults, practically just as accurate as professional diagnosis.

Edit: also I've been self diagnosed as having synaesthesia since my early 20s, was later confirmed and I even participated in synaesthesia research as a subject for three different entities. So, I disagree with you, especially for mental stuff. There is a lot of room for error but from there to say self diagnosis is bs, that's a stretch

In countries without free and efficient health care? Hell no. I am against self medication for obvious reasons, but my self diagnosis(On autism and ADHD), and discussing it with my doctor (Not telling the doctor "I have X and Y", but telling them "I think I might have X and Y but haven't been able to follow through with all the hoops they make me jump through to get diagnosed) got me the push I needed to actually go ahead and pay to get properly diagnosed.

Mostly because I thought "I am already an adult, so it won't make a difference", my GP asked me a few questions, told me he wasn't legally qualified to diagnose me, but recommended a private clinic where they did walk Ins, was pretty affordable and I would not have to worry about the main reason why I wasn't tested and diagnosed yet, the fact that my country's free health insurance gives those appointments after a grueling process of going for a general evaluation, scheduled months into the future, then having to bring the medical reference to a different city,, waiting for them to be approved, then get the reference + the approval to another office, which would then set up your appointment about a year after that date. Go make 10 people with ADHD and no help try to follow that process by themselves, which I tried and failed multiple times, and tell me how well it goes.

Oh, and I forgot to add, everything is valid for just 10 days after it is released from their current step, to bring to the next step, if those 10 days run out, start over from zero. Doing that while also having a full time job, which falls at the same time as the times when those offices open, recipe for absolute disaster.

I'm on the camp of, "offer the self diagnosed support but encourage them to get diagnosed before actually treating them", and not only "You're supported" clichés, actually get in there and help them with all the red tape and paralizing issues they will end up facing, and the reasons why they haven't been diagnosed yet.