My mom has a non-autoimmune related health issue (Costochondritis) that has been difficult to diagnose and she's been dealing with that for the last 7 years or so. It sucks having a health problem that no one can diagnose. Even in the case where you don't have a mechanical issue, the pain is still real.
My concern is that for every person with a rare disease causing vague symptoms, there are more people with similar vague symptoms that don't have an underlying rare disease. When you tell people things like "keep going to new doctors until you find one that believes you", or "do your own research", or "use my AI tool that I diagnosed myself with", those people who don't have an underlying disease will do those things too.
And if they do enough tests, or see enough doctors, they'll eventually get a diagnosis. If they see enough doctors, and push hard enough, they'll eventually find a quack who will do all kinds of procedures on them.
One of my mom's friends was convinced she had endometriosis, she doctor shopped for years until she found someone willing to do surgery in a city several hours a way. She still suffers from complications from the surgery, and her other symptoms are no better off.
I know of a kid who came very close to dying from an infection because his parents were convinced that he had chronic Lyme and they doctor shopped until they found someone willing (but not qualified) to install a central line to administer antibiotics.
Even if you have an underlying condition, doctor shopping and doing your own research is no guarantee that your eventual diagnosis is the right one.
I'm not saying you shouldn't advocate for yourself. Nearly everything is a continuum, but when you cross the line into "Doctors are idiots, only I can diagnose myself territory", you're headed into dangerous waters. Educating yourself is fine, diagnosing yourself is the problem.