Healthcare insurance isn’t the same as healthcare.

Medicare for All, Medicare, Medicaid, public / private / employer insurance are all systems for reimbursing healthcare providers. They do not guarantee that the care provided will benefit the patient or be cost-effective. The foundational step is to create and maintain a rational healthcare system. In the meantime, a rational government will take measures to ensure that no one is denied adequate coverage for necessary treatment because they lack the funds. But in the long run, there’s no point perfecting the reimbursement system without first deciding on who and what should be reimbursed.