Most of your complaints seem to revolve around just presidential primaries. I’m not gonna argue that it’s stupid how they do it but it’s also just one position.

Why are people not voting in every single primary for local and state positions too to get left leaning candidates as the Dem candidate? Congresspeople have far more weight and more impact than just the president. Witness the overton window shifting far, far right due to crazy Tea Party and Freedom Caucus candidates, etc. etc.