If we had robot doctors, we would then sue the builders, programers, maintenance companies, etc.
Also, are we suppose to have robot engineers, teachers, police officers, cooks, bus drivers, pilots, etc., etc.
Yes, if a doctor is high or drunk they are liable. They could also liable if there mind wasn't on their work, they were trying to rush through to get another patient, just tired because they had to stay up late to watch the big game, or maybe life's problems. As professionals, they should decline to give service if they are not up to being able to do it. Any professional is to do this even if it is woman that makes $5 an hour to cut your hair or a truck driver for a few examples. That is why states license many professions and one thing that is common with all professions is you have certain legal responsibilities to meet.
The issue with lawsuits is what is the life or injury really worth? Then add the lawyer fees on top it. Also, was it really the doctors fault? There are many unforeseen circumstances that a doctor could encounter. It is a very large gray area there. Then what is the life worth? Is an 85 year old grandfather's life worth the same as a 30 year old father of 2? How exactly do you calculate the value?
It is what you learn, after you know it all, that counts.