I absolutely agree, the way health insurance works in the US is completely broken. In a flood insurance it's simple, floods are singular events, if you had insurance at the time of the flood you are covered, if you didn't you are not covered (US flood insurance is broken for different reasons, but that's beside the point). With health that doesn't quite work, any system that allows people to enter and exit health insurance at their leisure is sure to be gamed by people who get insurance only while they have health problems. That leads to insurances having the power to screen and reject people, leading to a whole world of hurt and inequality.

The reasonable way to run health insurance is what most European countries do, with various implementations: you get health insurance when you are born, and you can't get out. That way the insurance can actually work as an insurance (averaging out risk), can't be gamed, everyone is covered, and if your work isn't your insurance you have a freer labor market.