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.
