There are lots of smaller points in this piece that I think miss the mark, but on the whole this is actually not a bad read on the problems in the DNC. Most notably that it's The party of the establishment.
It's written as though no one could ever agree with a progressive policy, and I think that makes the author only see the DNC as too progressive for many, and blind to the fact that it's not progressive enough for many others.
Largely, I think the DNC has become the party of status quo and Not-Trump, and clearly that isn't good enough