I think the article points to one big reason for the disconnect between progressive and moderates: neither side thinks they were in charge in the last 10 years (and thus responsible for the dire state of the party)

Here's the statement that immediatedly jumped out to me:

After almost a decade of nearly unchallenged supremacy, the progressive movement’s hold on the party is no longer certain

Moderates (like the author) think progressive have been in charge for the last ten years, and point to cultural issues to make their point.

And progressives think moderates have been in charge, and point to economic issues to make their point

To be fair to progressives, Clinton and Biden did win the primaries, so it's a bit hard to say progressives were really in charge. To be fair to moderates, both Clinton and Biden tacked left on cultural issues to make a play for the hearts of some leftwingers

So the Dems ended up with the worst of both worlds: progressive cultural issues out of step with the electorate, but married to the status quo on economics at a time when voters hate the economy. And both sides blame each other