If that were to be the case, why does my insurer try to wiggle out of paying me based on shit like bogus claims of 'preexisting conditions'? That doesn't sound like something dome in good faith.

Good faith means that if you have a pre-existing condition then you disclose it, and it means that if your insurance company doesn't insure pre-existing conditions then they disclose that. This is all before signing the contract.

It doesn't mean there can't be robust discussions about what the contract covers when particularly unexpected sets of facts come up.

When I break a tooth, that's not due to a preexisting condition though, and them arguing that it is is bad faith.