There's really strong diminishing returns in healthcare. Improve hygiene, chop away obvious cancer, a dozen other simple types of surgery, and basic meds in obvious cases? Stuff like that probably gets you 60% to where contemporary best practice is, for 5% of the cost. Autonomous LLM doctors would fit in great here.
And in developed countries, a medically trained LLM as a "second opinion" is IMHO an excellent use case of the technology. Provided the doctors managed to maintain medical thinking, keep up to date with their own knowledge, and bother to look into patient histories to the same degree as before. Which is a big if, they're only human too.