Anecdotal data point about primary care:
About a year or so ago I subscribed to "direct/concierge primary care practice". I pay $80/month and in exchange getting an access to a primary doctor who takes care of keeping an eye on me, my blood pressure, all my prescriptions (some of which used to require monthly visits to specialists). I am also getting access to really cheap prices on labs, typically 30 min visits same or next day if I wanted (unlimited visits per months), EKG when I wanted to put my mind at peace right there in the office ($25 one time fee), etc. Doctor is available over the phone, text or email. Does not dismiss me when I mention "I've read on internet..." something and actually explains things. Basically, I think it will take care of the most of my health care needs, as well as puts my mind at ease thanks to easy access to the doctor.
The doctor also refers me to specialists who's cash-prices were often below my co-pays.
For major accidents I still have a traditional health insurance with high out-of-pocket limit bought at the marketplace (self-employed).
This practice existed for quite some time and thanks to the subscription-based fees (not episodic described in the article), I expect it to be a long-term sustainable business. It is also owned by the doctor as far as I am aware. They explicitly do not deal with private or public insurances. (Although by recent law changes I can charge monthly fee to HSA account).
There are a few practices like that in the area. Can't say if others are similar in experience, but fees - are. So it looks like it is possible to build sustainable business around primary care. But it takes a different approach.