Insurance is, at its core, a reasonable halfway measure towards public control of a critical resource. If you need something only very rarely, but it's something that needs to exist ALL THE TIME just in case, insurance allows you to pool your resources with other people in the same boat and afford to keep an industry around just in case. Somebody will always be using it right now, and it'll be there when you need it, because you paid into the pool.

The problem is, as always, the insertion of capitalism into the solution. If someone has to profit from this set of relationships, the motivation to provide the resource is in competition with the motivation to extract more profit. This is what happened to healthcare.

Insurance is only a halfway measure because we already have an organization capable of managing common resources that individuals use only rarely but which the public needs all the time: that organization is the government, or the governments at various levels. We manage lots of things this way: fixing roads, stopping houses from burning down, pulling people out of floodwaters, that kind of thing. You don't need it all the time, but it's there when you need it because you're paying taxes to a government that has no profit motive from it. Insurance should only ever have existed temporarily while government infrastructure was debated and organized, but the for-profit industry managed to capture enough of the government to keep itself alive indefinitely.

In short, insurance isn't inherently bad, just not meant to be a permanent fix. Capitalism is bad.