> You seemed to have missed the part that said "the ACA's individual mandate, which is the foundation on which guaranteed-issue health insurance works.".
Starting with a premise that that ACA is working is invalid.
In the current US health care system about 49% of people get coverage through their employers, 19% are covered by Medicaid, 14% are covered by Medicare, 2% are covered by other by other public plans (ex: VA), and 9% are uninsured (for various reasons including not being mandated to get coverage). That leaves 7% of people that get coverage on the individual market[1].
On average, the cost to insure people in that 7% is substantially higher than the 49% receiving coverage through their employers. That's for a variety of factors including them being statistically unhealthier (unemployed people tend to be sicker) and more broadly because employer's generally provide coverage through self-insurance that removes all profits from the equation. Large employers don't just buy coverage from Anthem or Horizon, they self-insure and buy an umbrella style master coverage to cover outliers.
That leaves a small percentage of the 7% on the individual market that are not receiving any subsidies to pay a grossly outsized cost for health insurance because they're bearing the costs of the wider 7% risk pool. That's what's broken in the ACA and that's who bears the full impact of the mandate. The policy as it stands now is destined to implode as at some point that top end of the market will actively avoid it anyway.
My solution to all of this is to ban employer provided coverage entirely and require the same open access provisions for health insurance to all plans. That would widen the risk pool substantially, eliminate issues with fragmented markets, and open the door for more job mobility (health insurance wouldn't be tied to your job). Throw in Medicaid for free at the low end and a public option with which one could buy into a Medicaid-lite to add additional competition in underserved markets and you've got a working healthcare system that can be layered upon our existing one.
[1]: https://www.kff.org/other/state-indicator/total-population/?...