A potentially easier fix would be to roll back the changes made to the US primary system in the 70s and go back to letting parties pick their candidates internally rather than throwing it open to an electorate where only the most partisan bother to vote in primary elections.

The old system had its share of problems but I think that, all in all, the old smoke filled rooms worked better than what replaced them. Using approval or ranked choice voting to have more than 2 parties would solve most of the issues with the system anyways and we ought to do that as well but that seems harder to get in place.