However, when you get sick that rate doesn’t go up, so there’s no incentive from your employers standpoint to fire you when sick. Because of the “losing coverage” part it’s still extra shitty when they double up (cancer plus being fired sounds pretty awful).
Obamacare notably created markets for folks not receiving health insurance through work to purchase it directly (in addition to subsidies for low to middle income folks to do so, and several regulatory changes around other parts of the system), but that basic system wasn’t fundamentally altered and has been more or less how the US has done things since world war 2.
Fun bonus fact, employer based insurance was first offered as a workaround for world war 2 era wage controls.