This is not strictly true. Health insurance has always been available for purchase by individuals, and the ACA expanded access to this by providing income-based subsidies. When you lose your job, you lose access to your employer's subsidy and risk pool.

That doesn't change the fact that heath insurance and healthcare is expensive, it's just pointing out that the only way most people can afford to have it is because their employer is paying for most of it. If that cost was more transparent to salaried people, it might spur a more useful conversation about how to bring down the cost of healthcare.