It's disingenuous to criticize Sanders for wanting a Medicaid-for-all program that "leaves it up to the states" while defending Obamacare, when Obamacare itself was designed to vest its biggest and most tangible changes with respect to lowering the rate of uninsured in the states as well. From working within the existing parameters of Medicaid and Medicare, to signing off on state-based healthcare exchanges, Obamacare's real-world, specific mechanics were very much state-based. Sure, some loose parameters are governed by federal requirements, but those were never designed to be the bulk of the benefit in terms of lowering the rate of uninsured.
This is an incredibly cogent point.