I agree generally with what you're saying as a good rule, I would just add one exception.
If you've seen multiple doctors, specialists, etc over the span of years and they're all stumped or being dismissive of your symptoms, then the only way to get to the bottom of it may be to take matters into your own hands. Specifically this would look like:
- carefully experimenting with your living systems, lifestyle, habits, etc. best if there are at least occasional check-ins with a professional. This requires discipline and can be hard to do well, but also sometimes discovers the best solutions. (Lifestyle change solves problem instead of a lifetime of suffering or dependency on speculative pharmaceuticals)
- doing thoughtful, emotionally detached research (reading published papers slowly over a long time, e.g. weeks, months) also very hard, but sometimes you can discover things doctors didn't consider. The key is to be patient and stay curious to avoid an emotional rollercoaster and wasting doctor time. Not everyone is capable of this.
- going out of your way to gather data about your health (logging what you eat, what you do, stress levels, etc. test home for mold, check vitals, heart rate variability, etc.)
- presenting any data you gathered and research you discovered that you think may be relevant to a doctor for interpretation
Again, I want to emphasize that taking your health matters into your own hands like this only makes sense to do after multiple professionals were unhelpful AND if you're capable of doing so responsibly.