I think if people learned more about the ACA and trusted that it, or something better, would exist until they become eligible for Medicare, they wouldn't be so afraid of leaving their employer health insurance behind.
That said, health insurance isn't quite the same as food or other necessities that people buy with their paychecks. Employers buy the insurance for their employees, usually at a very significant discount, and often a better quality than is available through the ACA exchanges.
I know the employer-based coverage I left last year had a lower deductible than all but a few of the gold plans on my local exchange, a lower out-of-pocket maximum than any of them, and there were no premiums for employee-only coverage. If those were the only material differences, all you need to do is save up some cash and the ACA will work fine for you. Health insurance is expensive and people who are used to heavily subsidized coverage from their employers often don't realize how expensive it is, but saving up for it on your own is possible even if you have a spendypants retirement with no premium subsidies.
There is one more wrinkle though. The coverage I had through my former employer would pay for routine care across the US. None of the ACA plans available in my area will do that. They all have networks narrowly confined to within the state of Washington and some have little to no coverage outside the Seattle metro area. They'll all pay for "emergency" care anywhere because the ACA makes them, but you can expect them to try and argue against anything borderline being an "emergency" at all. Of the six companies offering coverage in my area, only one (Kaiser Permanente) will even cover urgent care out of network. None of the companies covers non-urgent visits. That's not a big deal for me and my healthy family, but could be a major source of concern if you have a condition that requires occasional routine services and you want to do any sort of extended travel ever.
Bringing it back to the food analogy, it's not just that your employer is giving you a discount on fancy meals, it's that the meals they're giving you aren't available at any price if you go it alone. Whether the less-fancy stuff will provide adequate nourishment depends a lot on the individual.