If the people with modest houses hire the same landscaper to take care of their yard as the massive mansions across the street, and notice that the landscaper hardly ever works on their yard, and half the time he shows up, he throws the trimmings from the big house on their lawn, it is not a purity test to say they are doing a shitty job.
It's a job evaluation.
Likewise, it is not a defense of the shitty job to say they are doing more for us than a gang of con men, who sometimes convince some neighbors to pay for lawn care, and then never deliver at all, or "take care of" their lawn with a flame thrower.
If elected Democrats and party operatives don't take criticism from the base of voters seriously--DEMOCRATIC PARTY voters, not swing or Republican voters, they will continue to struggle and just barely win.
Also, if you are not loyal to those who working and middle class people who are members of your own party, why would swing and conservative voters expect you to take care of them?
The New Dem/DLC/Third Way wing of the party does push for some progressive change. The problem is, too often the progressive change is structured to give the financial sector or some other corporate interest a big chunk of the money that was supposed to go a program to help the rest of us, when the government itself could deliver the program more cheaply and effectively.
A good example is Obamacare. Many aspects of the private insurance part were huge improvements. But the Medicare portion is more efficient and costs are driven up by the avarice of spoiled trust fund babies. Those insurance companies don't even seem grateful that Democrats delivered tens of millions of new customers to them, and keep jacking up prices to pad their profits.
If the only consideration was delivering healthcare at a good price to average Americans, there should have been a timetable for all health insurance companies to rein in their overhead or Medicare would start expanding until it covered everyone.
That kind of accountability would make giving the private sector a role more palatable because it would make it clear that in "public private partnerships," the public part was in the driver's seat.