Thing is, the Democrat party can't get a single soul elected most places in the US. They need unaffiliated voters, too. The balancing act they need to play is one of placating their base while not turning off the middle.
The one variable that keeps getting left out of discussions like this is rampant vote fraud. Nothing is being done to stop it. It gets worse every election. It was disastrous in 2018, probably at least half a dozen seats in the House were lost by vote fraud. It will be much worse in 2020.
Vote fraud in much of the United States has reached third world Banana Republic levels.