It is your duty as a scientist to provide empirical evidence.
That I agree with. As long as it doesn't necessitates placebo controlled trials, which would kill the study subject at hand from the outset.
However, in my experience with Cardiologists, Internists, Pulmologists, or any General Practitioner, young or old.. I had to learn that none of them had learned to read studies and verify them for themselves. In discussions they exhibited that they don't understand such simple concepts even every chronic disease patient should know about, for being enabled in making informed decisions. Like what's the difference between relative and absolute risk reduction, primary or secondary prevention, number needed to treat or harm, etc. Therefore I must assume the training to become an MD is very far from that of becoming a scientist, unless she or he had that particular inclination already in youth.
Now such a MD himself might get disabled in the middle of life, and because of the shortcoming of his training as MD, turns to the functional medicine approach instead to recover oneself. Being glad having overcome one's disability, she or he shares the few last years as an MD with his patients with all the enthusiasm about what was learned additional to the training as MD.
Now you expect from such a person like Mark Hyman at age 59 short before retirement - or at any other age - to start a career as a scientist?
I don't think that's anywhere realistic. Nor should anyone feel above any other and entitled to demand what she or he should pursue in life. Or depreciate an others vocation because it doesn't fits with one's own needs.
I personally try to have a livelihood where I at least do not harm anyone. Repeatedly I had to refuse treatments offered by MDs because of possible harms, of which I had to inform myself elsewhere. They seem to have forgotten: 'First, do no harm!'. Any MD who remembers that through whatever tire circumstances in my eyes has gone full circle, and deserves all my respect.
The average burned-out middle-aged MD isn't a scientist to begin with. Take Dale Bredesen or Martin Lerner as examples who perused a scientific career from the start.
@pamojja, I really do not see why you are making excuses for functional medicine's shirking of its scientific responsibilities.
Scientifically inclined youngsters will show up in the future. You have to grant any individual, who out of disappointment with conventional medicine turns to functional medicine, the same right of choosing one's vocation, as everyone grants to you. Appreciation of individuals is a better motivator than depreciation.