Hmm...

The ketogenic diet is not considered a benign, holistic, or all-natural treatment. As with any serious medical therapy, it may result in complications, although these are generally less severe and less frequent than with anticonvulsant medication or surgery. [...] Supplements are necessary to counter the dietary deficiency of many micronutrients. [...] Like many anticonvulsant drugs, the ketogenic diet has an adverse effect on bone health. [...] In adolescents and adults, common side effects reported include weight loss, constipation, dyslipidemia, and in women, dysmenorrhea.

Sounds like you're right, this diet is something that should be done for specific medical reasons, with professional guidance and with specific goals in mind:

The ketogenic diet is a high-fat, adequate-protein, low-carbohydrate dietary therapy that in conventional medicine is used mainly to treat hard-to-control (refractory) epilepsy in children.

https://en.wikipedia.org/wiki/Ketogenic_diet

My doctor said something similar.

But after years of me being on keto, losing 167lbs, having an "absolutely fantastic health record" and the "healthiest bloodwork" he's ever seen (his words), plus significant improvement in mood, memory, and mobility, and a significant reduction/elimination of pain and inflammation, he changed his mind.

He even said that most of the content he had heard or read when saying it was "a bad diet" all those years ago was "completely biased" and "worded very slyly" (also his words). After revisiting those sources, he realized they "weren't actually describing real keto, just people eating a ton of fat" (which is not what keto is), "and crying about how bad fat is" (again, his words... which made me LOL). Also, mega bonus points for him - he actually checked into the sources and found that most of them were funded by the sugar industry.

It takes nothing to realize you're wrong; for some people, it takes a lot to admit it. He had no problem doing so, and even recommends the diet to other patients now.

Some nits to pick:

Ketosis is a metabolic state where the body burns fat for fuel (lots of handwaving, but more or less)

ANY diet where weight is lost MUST have states of ketosis to metabolize fat (by definition). This includes the old classic 'eat less, move more', 'count calories CICO', 'low fat diet' etc.

A ketogenic diet, keto for short as people use it, is a diet that keeps people in the metabolic state of ketosis for extended periods of time. There are food groups that do not introduce glycemic load (fat and protein), and therefore keep the metabolic state of ketosis.

I must respectfully disagree with the statement that keto isn't safe - if that statement were true, then losing any weight ever, would not be safe - including sleeping (you run out of glucose and burn fat while you sleep.... break-fast is called that for a reason). The flip side of the 'keto isn't safe' statement is the implicit statement that carbohydrates are a essential macronutrient - which is an difficult position to defend.

If we modify the statement to be prolonged periods of ketosis are not healthy, then we need to answer how long, and what levels of carbohydrates are essential. We would also need to account for the metabolic success of cultures that do not consume carbohydrates (historic Inuit for example - who lived in cold regions where no grains grow).

Keto seems less dangerous than the old Atkins diet. I had a coworker who rapidly shed about 30 lbs on Atkins and then had a stroke - he was 32.