Without making a claim about whether it's what most people actually want or not, there's not much that an individual can do about this by changing their voting

Without making a claim about whether it's what most people actually want or not, there's not much that an individual can do about this by changing their voting preference. The US doesn't have proportional representation, and the overwhelming majority of elections are "first past the post" rather than one of the more "modern" alternatives like ranked choice votes, so in practice very few elections ever swing to anyone outside of the two major political parties (neither of which have a particularly large contingent of politicians who have come out in favor of something like single-payer healthcare). Even for a purely single-issue voter who only cares about this, from a game theoretic perspective you're likely to be essentially throwing your vote away if you vote for someone outside of those two major parties because it's unlikely enough others will. Presidential elections are even worse because they're determined by electoral college vote rather than popular vote. Even ignoring the potential for "faithless electors", all but two states allocate the entirety of their electoral votes to the candidate who wins the majority of their vote, which means that if you live in a state with a majority who reliably vote for a specific party's candidate every four years, your vote for president is effectively meaningless. The only obvious way to fix these issues with how elections work would be to elect people who make different decisions about how to run them, which is hard to do because of the issues themselves. The system is self-reinforcing in a way that makes it extremely difficult for the average person to do anything about it, and any desire to do so gets weighed against the concerns about the policies that you might actually get to influence by voting for one of the two candidates who might actually win. At the end of the day, people who are concerned with the fundamental systemic flaws in things like elections and healthcare still likely end up picking pragmatism over principle (with the expected value of a vote for a candidate who is almost guaranteed not to win being lower than one who is might be less desirable than a third-party one but still has an actually realistic chance of winning and is preferable to the other major party candidate) or just check out of the system entirely (with people not bothering to vote at all already being a fairly common phenomenon in the US).