Without malpractice insurance, would doctors be incentivized to not take on risky patients? Risky could be defined as litigious (I know this patient has sued another doctor before) or medically difficult to treat (this patient needs this surgery but they are at high risk of poor outcome due to their current state of health).

Having sued a doctor once, you might never be able to get medical treatment again.

Which would also disincentivize ridiculous lawsuits that you'd almost certainly lose.

It would also disincentivize legitimate lawsuits.