Last time I went to the poll (absentee ballot of course) there was this democratic (small d) institution called the primary election. Many leftist Congressional candidates have ousted the traditional Democratic incumbent (not in my red state, maybe), which of course moves the party leftward (for better or worse, depending on your political theory). So if you don't like this year's slate, there's time to choose and run a more progressive candidate for next time. If you haven't planted a garden in the spring, there's no point in complaining about the lack of good food in the winter. "Vote Blue no matter who" just means you haven't done your homework--it's not an inherent flaw in the system. And no, voting for Bernie Sanders, and sending his campaign a few piddly donations, and posting a few tirades to Facebook doesn't merit a passing homework grade.
But anyone who doesn't want to undertake the slow, hard work of party reform can just torch the Democratic Party and start their own. If the thesis of this article has any credence, a good way to destroy the Democratic Party is to vote for Biden.
There you go, win-win!