The issue is not about preserving knowledge or saving the field of traditional medicine. The issue, in my opinion at least, is ensuring that people have enough knowledge and experience working with patients to ensure that 1) scientifically accurate, correct, and beneficial information is being provided to patients, and 2) that the practitioners are competent enough to accurately diagnose conditions and treat them effectively - including with traditional medicine and referral for more radical interventions if necessary.

Which is why, in order to get a license to practice, my wife had to pass the medical boards and the naturopathic boards. For the medicine she's allowed to practice, she's held to the same standards as MDs.

1) it isn't clear to me what actual "training" NDs have completed, making it difficult for me to actually assess what they should and should not be doing,

It varies per state. Many states don't license at all, so anyone can call themselves an ND. In California my wife is allowed to call herself a doctor, but not a physician because of existing liability and insurance law. In Washington she can be a part of HMOs and take insurance and be referred out to like any other specialist. On the other hand, buddy of mine lost his best friend to a "naturopathic doctor" in Hawaii that tried to treat his cancer with herbs and well-wishing. The twist? He was also an oncologist.

2) the quality seems to vary widely.

See previous statement about state law. There are seven schools that teach to the test that the AANP hammered out with the AMA. There are quite a few that don't. Those seven schools are the only programs that will get you a license in a licensed state. Everyone else is a charlatan.

How does a ND learn about the diagnostic process and develop clinical reasoning?

A year of gross lab, two years of residency, a year of pharmacy, O chem, microbiology and all the rest. Same as an MD.

What is their clinical training? Do they know how to do a basic physical exam?

Three mandatory years in clinic seeing patients while still in school does the trick.

There are others - many others, if the number of times I've heard shitty and outright dangerous advice from patients provided by NDs is indicative of anything

So you're in Germany, yeah? I have absolutely no idea what the regulatory constellation is out there. I only know the US, some of the UK and Australia/NZ. I know that the UK, Aus and NZ are a lot more lax by comparison.

instead, it becomes a crusade against "traditional" medicine and some kind of pseudophilosophy that claims that some kind of herb extract or acupuncture will cure cancer

Yup. And those are the ones that make the headlines. "Parents refused treatment for their daughter; preferred homeopathy" and the like. Never a happy ending for anyone.

My wife had a bad case of eczema her first year. She had an instructor that decided to treat it homeopathically. It got really really bad - which excited the hell out of the homeopath because she was having a "healing crisis." Never mind that her hands looked like she'd been soaking them in gasoline overnight or that she couldn't make a fist without crying. That was Reality Intrusion #1 - I told her that no "healing crisis" was worth this and made her professor give her a steroid cream. Reality Intrustion #2 was a bladder infection they tried to treat with cranberry juice and herbs well past the point where it was clear it wasn't doing anything. She ended up with a Cipro prescription. Has she treated bladder infections with cranberry juice and herbs? Yes. but not all of them.

Pragmatism is important in any branch of medicine.

NDs and other pseudomedicine practitioners (chiropracters, for example) are quick to take on the title of "doctor"

The argument in the US is since you can get a doctorate in philosophy, you can get a doctorate in homeopathy. But unless you've got an MD, you don't get to call yourself a "physician."

And while I share your interest in placebos, I think it's important to remember that placebo effects really aren't the basis for a general treatment strategy. Multiple studies have demonstrated that while placebos typically result in improvement in patient-reported outcomes, there is no statistical difference between placebo and no treatment in most cases.

And I think it's important to point out that the overwhelming majority of patients seen by naturopathic doctors in the US tend to be the "worried well" who likely don't have anything physically wrong with them to begin with. Establishing that this is in fact the case through blood tests and other empirical evidence is important... but beyond that, statistics goes completely to shit when your n=1. That, more than anything, is what I believe has led to the rise of alternative medicine in the United States if not the world: the fundamental belief that patients will revert to the mean if given long enough, rather than recognizing that anyone who has seen a dozen specialists without finding relief is, by definition, a corner case.

In other words, your sugar bill is probably not going to cure your IBD, cancer, hepatitis, or other serious condition beyond possibly making you feel better.

So wouldn't you rather have your sugar pill dispenser be fully trained to recognize and refer IBD, cancer, hepatitis or other serious maladies to a specialist who can treat them effectively?

My wife much prefers delivering babies to naturopathic care. For the former, she's got "we're having a baby and there's a 4 in 5 chance that it'll be totally normal! Take our money!" For the latter, she's got "I've seen half the specialists in the LA basin and none of them have been able to help me. Your turn." The only saving grace of the naturopathic patients is that they've long since conflated "make me better" with "make me feel better" and by the time they've been told there's nothing wrong with them by six specialists, someone who listens and tells you to get more sleep goes a long way towards empowering you towards your own health care. But she is nobody's PCP. She does well child visits, she deals with chronic conditions, and she practices adjunct care in support of oncologists, endocrinologists, psychotherapists, etc.

And I guarantee you, the more education you have about what you don't want to get into, and the more professional stakes you have on the line for getting in over your head, the more incentive you have for practicing what you know.