People always complain about those structural things but don't actually want to exercise the immense power they have right now: voting in primary elections. Primaries have abysmal turnout rates, and given the geographic self-sorting and gerrymandering, serve as the de facto election in most places. Politicians know their real constiuencies are the 10% of people who turn out in primaries. Those are the folks they're afraid of. Everyone else is ceding that power by not participating.
In a lot of states, primaries require registration/party membership to participate in. Effectively more gatekeeping. Additionally, the two parties have no interest in breaking the two party power struggle.
To the best of my knowledge, party registration in closed primary states is just an additional question on the voter registration form. It's not exactly an onerous cost unless you're someone who regularly switches which party's primary you want to vote in.
That said, even in open primary states, primary election participation is low outside of presidential contests. I served as a poll worker once for a US House/Senate primary, and my precinct got about 7% turnout, and I'm in an open-primary same-day-registration state.
More than that, though I agree with everything you're saying, is nobody even considers congresspeople in these discussions. Everyone focuses on the president and how they appoint the judicial, congress is where everything (read: nothing) happens.
"Santos ran as a Republican for the United States House of Representatives in New York's 3rd congressional district, against Democratic incumbent Tom Suozzi, launching his campaign in November 2019.[24] Normally, the Nassau County Republican Committee, known for the tight control that its leadership exercises over often competitive races for its nominations, would have discouraged an unknown candidate with such minimal experience. However, Suozzi was expected to win the race easily, and no other candidates had put their names forward."
If you otherwise meet the requirements for the seat--citizen (usually), resident , not a felon--you too can find a ballot line for a contest a party expects to lose.
I should add that I have no idea whether Santos actually was on the primary ballots.
In terms of services the government provides, overall quality of life, etc, I'm not sure how much/if the US is ahead of, say, Botswana. I know that we're basically the wealthiest of the unhealthy (excluding tiny oil states like Bahrain), and it wouldn't shock me if you could describe the US as the wealthiest country in the world with a third world standard of living, especially as the lines between first and third world get blurry.
I don't have the data or time offhand, but if you're interested, have a look at ourworldindata.org; they probably have many relevant things.
They could just choose blanket primaries, like California has: https://en.wikipedia.org/wiki/Nonpartisan_blanket_primary After the blanket primary, the final election is between the top-two, regardless of their party affiliation.
The effect in California seems to have been to make the state even bluer, but arguably that's because rather than being forced to choose between Republican and Democratic standard bearers, the system returns some advantage to more moderate candidates, just within the field of Democrats (increasingly many of whom were once registered as Republicans). Unless you want to run on stereotypical Republican issues (abortion, religion, etc), your best bet strategically where the electorate is already majority Democratic is to run as a Democrat, regardless of your policies, which is not an option where candidates have to worry about being "primaried".
Ranked-choice is even better, of course, but I think you can see a similar dynamic wrt the candidate pool shifting Democratic.
I'd argue Alaska's system is even better. They have a top-4 jungle primary. Everyone focuses on the ranked-choice voting general election they have that follows, but I think letting 4 candidates advance out of the primary is an improvement because it weakens the primary electorate's power to eliminate candidates early. And as mentioned, the primary electorate is tiny and probably not representative of the population as a whole.
People are - but then they run into the same corruption that has warped general elections [1]. They also run into the issue that primary elections in the US are arranged by the political parties which are also part of the corruption.
The problem is our electoral system is a sham. Not just the mechanics (FPTP aka plurality voting is one of the worst systems) but the concept of "money=speech" which is really "money>speech". The 2 party system actively disenfranchises 30-50% of the electorate. The electoral college narrows the Presidential election to a half-dozen states. Gerrymandering warps whose votes actually matters. The list goes on and on. And most of these problems are present in primaries as well.
