The vast majority of employees are not in a position to simply quit.
I get that; I have plenty of friends, married with kids, in that position. At least the ACA is in place to make health insurance more portable, even if it's not as affordable as originally intended (thanks Republicans), so there is one less thing tying people to their current job. Universal health insurance would be a step up in that respect, like Bernie Sanders' Medicare for All. I'd even support a reduced Basic Medicare for All with the ability to purchase something like medigap to cover extra things. I think the EU system is probably better for workers, but, of course, the taxes are higher to pay for that and Americans hate paying taxes, even if they get something for it. Unfortunately, I think it's a "other people don't deserve things and I don't want to pay for that" mindset rather than "we're all in this together" one.