You at first appear to say that gathering data and automating things is hard and might not be possible.
Then here you're saying that checklists, evidence-based guidelines, and improved interoperability between systems are all the source of doctor improvements.
These are all arguably forms of AI that have been created through data gathering. Yes, a checklist is a very boring AI, but it's taking some knowledge out of the heads of a group of people and then making it available for someone else to use. The missing step seems to be that instead of having a person look at a piece of paper and execute the checklist and evidenced based treatment, having a computer do it.
Now we're talking about cost. Cost where (at least in the USA) going to the ER for a broken bone can cost thousands of dollars. Cost where (at least in the USA) a birth (something people from all walks of life go through) has a minimum of the patient spending $10K and regularly gets into the $50K and up range (not even talking about ultrasounds etc leading into the birth).
I cannot believe that we're really talking about data collection being too expensive for the medical industry. Maybe nobody wants to be the person to pick up the bill. But it's going to be a rounding error of a rounding error compared to all the other money that goes through that industry.
As for diagnosing rare or very rare diseases, yes, it is possible, as you said. However, if you search for the rare disease I have in PUBMED, there are only 111 journal articles that have been written about it, and some are in foreign languages. The information on it is very sparse. I also doubt that it would be diagnosed by AI, as it effectively looks like "diabetes complications" (I have type 1 diabetes) and even though I had autonomic neuropathy at age 5, the onset of symptoms was very insidious.
Diagnosis isn't particularly difficult or time consuming in most routine cases after gathering the necessary data. If you see a jagged line on the x-ray then the patient has a fractured bone. If the A1c level is 7.5% then the patient has diabetes. Etc. Improving diagnostic accuracy will help in rare cases and is worth doing, but that won't have much impact on the health care system as a whole.