I don't think you understand their point. Republicans always turn out to vote for their candidate. Then they win (at least a good portion of the time) and they vote in primaries and move the party further right. For any evidence just look at the past 2 decades.

Whereas the left just decides to sit out and therefore Dems lose (or only win at odd times.) They can't count on leftist/apathetic voters, so they go towards where they think they can get votes (ie. people who always vote and if they do convert enough they are profiting by gaining one vote for them and removing one from Republicans.)

Now everyone here is saying it's soooo obvious that it's a poor strategy but is there any introspection on behalf of the left/apathetic? How has withholding your vote or not voting in primaries gone? It's been done for years and society has moved so, so far away from leftist goals no?

So their point is that it probably is a mix- surely the Dems need to actually run on popular policy and leftists/apathetic need to suck it up, vote in all elections, and vote for the best candidate. Pick your preferred candidate in the primary and then vote for the Democratic candidate in the general, no matter what (well- barring something egregious like...being anything like Trump.) Once Dems actually have power, you can keep pushing left. But if people just sit out, you're not gonna be counted. Decades of that is proof.

Edit- maybe you mean you can't win the center over with conservatism-lite. Maybe that's true, maybe not. But someone mentioned Bernie finished behind Harris in Vermont so I don't know that it's a maxim.