Anyone worried about house fires could simply wait and, if they did have a house fire, sign up for my insurance after the fact.
This is why pre-existing conditions are "special" - they are fundamentally incompatible with a free market insurance system. And it is, partially, why American insurance was cheaper previously - insurance companies could simply deny expensive customers and let them die to keep premiums low for the healthier subset of the population they covered.
Republicans were elected to get rid of the "bad part" of ACA - mainly the individual mandate. Saying you want to get rid of that is the exact same thing as saying you want to re-introduce pre-existing conditions, they go hand-in-hand.
Either we deny coverage to those that are already ill, or we force everyone to have insurance (ACA, single payer, public option, whatever).