Sure let me just wait 10 years to see someone.
Thats what its like and even a psychologist can be wrong, people that self diagnosis isnt just doing 5 mins of research it's often years or months of research.
I think that after personal research it's perfectly viable to say you believe you suit the criteria for a diagnosis, that you think you may have something, then you can then use that information to make the symptoms easier to manage.
But people spend years in school in part for the purpose of diagnosing as accurately as possible, because it is important to note that they have a firmer understanding more things than just the singular diagnosis you may have been hyperfocusing on, as OP said, its very easy to convince yourself you have something when you are looking into only that thing especially on the internet. Plenty of things have overlapping symptoms and part of becoming a doctor in any capacity is learning to say "could be these things, and I doubt it's those things"
Doctors can be wrong, yes, I agree, and if you believe a doctor is wrong you should seek multiple opinions, by other doctors who have spent lengthy periods of time in school learning how to identify and rule out other diagnosis.
tl;dr: the healthcare system can definetly suck, but I still think that you shouldn't self-diagnose and take it as gospel, but I have no beef with self speculation especially if that leads to better quality of life.
edit to add: I do think, though, for minor/common stuff it's reasonable to say "I have deppresion/anxiety/a cold/a migrane" without needing a doctor to back it
