Some people will be miserable no matter who is running
Just to point out… many people don’t care about the Democrats, except as a bulwark against the even more right-leaning Republicans. It’s not an institution that they respect and admire, but one they grudgingly tolerate.
I only joined the party so I could vote for Bernie in the 2016 primaries! 😉
If people want a shift to the left, they have to make sure that the Democrats crush the Repulicans for a few election cycles so that the Overton window can stop moving right and go left instead.
Unfortunately, the Repulicans are voting in a united front every election, no matter what.
The Democrats are notably terrible voters. They don’t show up like the Republicans do.