How is it a subsidy if, for example, the repeal of obamacare mandated that insurers accept back previous customers without restriction? But more importantly, why do you find that very small subsidy (if you think it is one) unacceptable, while there are other subsidies that are probably 100 times as big happening via Medicare and Medicaid? If you want to be an absolutist, be one and get the government out of healthcare entirely.
As for preexisting conditions, requiring a new insurer to accept preexisting conditions is a de facto subsidy by those other insureds who do not have the conditions but are paying higher premiums to cover the costs associated with such. And to have the federal government cover the costs of insuring the preexisting conditions through a private insurer in the alternative would put the taxpayer on the hook for it, i.e. another subsidy.