Part of the problem is that our primaries are weird. Primary voters tend to be more extreme (left and right) and when moderates show up to vote in the election, they're upset there's no moderate choice. I was talking to some colleagues from Australia and not voting is a fine. Makes primaries much more representative of the actual election when you get everyone to vote.
There are no primaries in Australia.
I've had the thought that the US primary system prevents any meaningful application of Ranked Choice, or other alternative methods. Currently there's no other proximate-choice candidates that make it to the general election; i.e., the case where Kamala and Bernie and Trump are on the General Election ballot can't happen in most places right now, which narrows the choice field significantly.