This is all too common among recovered patients. They did X and then they recovered. Therefore, they feel X must be a cure. Then they fall victims to confirmation bias and proceed to become a disciple. It would serve them well to keep the possibility in mind that 1) their recovery may have happened regardless of X and 2) there are likely thousands who tried X before and did not recover.
That said, my attitude always has been: why not try X if it is cheap and is safe enough? Cheap meaning a few bucks for a box of Sudafed, for instance, or safe like a diet change. The pay-off is great in an off chance that it works. Who knows, you could have one of the rare subtypes with a cause that can be cured by X. I remember seeing an interview of a woman who claimed to have recovered after a diet change. She wasn't proselytizing and she seemed to be unaffected. Which made me to think, maybe, just maybe, gut biome problem could cause ME/CFS-like symptoms in some people.